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tommac
2009-Nov-23, 07:49 PM
Can someone please provide the mainstream definition of anti-gravity?

R.A.F.
2009-Nov-23, 08:04 PM
Since there is no evidence for the concept of anti-gravity, your question is meaningless.

tommac
2009-Nov-23, 10:10 PM
OK ... what is the Ricci Tensor? Is that the tensor that defines the curvature of the topology in GR?

DrRocket
2009-Nov-23, 10:38 PM
Can someone please provide the mainstream definition of anti-gravity?

It is a figment of your imagination.

DrRocket
2009-Nov-23, 10:41 PM
OK ... what is the Ricci Tensor? Is that the tensor that defines the curvature of the topology in GR?

http://en.wikipedia.org/wiki/Ricci_curvature

Topology does not have curvature per se. Curvature is associated with geometry. Two manifolds with very different curvature can be topologically isomorphic (homeomorphic).

Rather than asking a bucket full of questions that you don't understand with answers beyond your present state of knowledge, you might try reading a no-kidding book and doing some study. For these sorts of questions a good book is Gravitation by Misner, Thorne and Wheeler. You might have to go back to a bit more basic mathematics before you fiind yourself ready to tackle differential geometry.

antoniseb
2009-Nov-23, 10:59 PM
Gravitation by Misner, Thorne and Wheeler. You might have to go back to a bit more basic mathematics before you fiind yourself ready to tackle differential geometry.

Fortunately MT&W has identified easy and advanced parts of every chapter.

DrRocket
2009-Nov-23, 11:12 PM
Fortunately MT&W has identified easy and advanced parts of every chapter.

They have identified two tracks in the book. One more rigorous than the other.

Neither would be a cake walk for someone who understands little mathematics and physics.

"Easy" here is indeed a relative term.

However, there is no royal road to understanding and MTW is as good as it gets.

asbakwod
2009-Nov-24, 12:51 AM
Basically, anti-gravity is removing the forces of gravity.

MrPibb
2009-Nov-24, 05:57 AM
Now isn't this the Q&A section? What about string/superstring theory with specific regards to gravitons? What if a higher order of sentience were capable of "transiting" gravitons between their naturally linked branes? Would mutability possibly not then be a very intrinsic trait of gravity as we know it? I'm not sayin' to go chasing fairy tales, but sheesh, show me your answer for the quantum field theory problem already so we can all be learned men.

sirius0
2009-Nov-24, 06:15 AM
I think this thread will actually answer itself.

Gravity: A mutual attraction between objects of substance.

Anti-Gravity: A mutual attraction of thoughts with zero substance :)

I wonder if there has ever been a thread specifically for those who need to go back and study a bit, to quote:



Rather than asking a bucket full of questions that you don't understand with answers beyond your present state of knowledge, you might try reading a no-kidding book and doing some study. For these sorts of questions a good book is Gravitation by Misner, Thorne and Wheeler. You might have to go back to a bit more basic mathematics before you find yourself ready to tackle differential geometry.


Fortunately MT&W has identified easy and advanced parts of every chapter.

There are a lot of resources on this forum for those who might want to take DrRocket's advice. Perhaps I should start one? What do you think?

Oh, and welcome to the forum asbakwod and MrPibb

MrPibb
2009-Nov-24, 06:54 AM
I think this thread will actually answer itself.

Gravity: A mutual attraction between objects of substance.

Anti-Gravity: A mutual attraction of thoughts with zero substance

Sorry to the OP for taking this thread as seriously as you apparently did.

Hilarious!:lol::lol::lol: But really, this guy may be fishing for kelp, but so what? If the good doctor above is continually disgusted by this guy's lack of knowledge, why bother to respond? What was in the previous post, something about a navel? Great for humor, but if you are wasting your time, then don't bother wasting your time?!:silenced:

MrPibb
2009-Nov-24, 06:58 AM
But in retrospect, I wonder if anti- gravity is strong enough to push a thread into oblivion?

astromark
2009-Nov-24, 07:56 AM
Tolerance and understanding. The need to be compassionate and to treat others as you would expect to be treated yourself... Single minded pig headiness is not a crime. The question is not silly. We have seen it before. Its been altered a bit but its the same idea. It has not been answered. That might be because it can not be. No such animal does exist. There is no anti-gravity. I will accept that you could remove yourself from the force of gravity. Its still there. There does not seem to be any proof of a force that could be construed as anti-gravity. No example of a white Hole has been found. No change in the procession of time has been found. No edge of the Universe, No Dark Energy, No dark mater... Higgs particle... Oops no hold the phone, That last one could be wrong... Its going again.:eh:LHC
As a mathematical concept it might be a feasible probability to reverse time or the force of gravity or both...In the real nuts and bolts world that we live on..Its not .
To those of you that find it amusing to ridacule... don't.
Use the science.It is why we are here... Its both real and kinder

slang
2009-Nov-24, 10:05 AM
"What is the Ricci Tensor?" to me seems one of those questions, where if you have to ask, you probably won't understand the answer.


Hilarious!:lol::lol::lol: But really, this guy may be fishing for kelp, but so what? If the good doctor above is continually disgusted by this guy's lack of knowledge, why bother to respond? What was in the previous post, something about a navel? Great for humor, but if you are wasting your time, then don't bother wasting your time?!:silenced:

Welcome to BAUT, MrPibb. There's quite some history from the person posting this question, and that's what some of the other posters may be referring to. This may not be obvious to someone who just joined the board.

MrPibb
2009-Nov-24, 05:28 PM
"What is the Ricci Tensor?" to me seems one of those questions, where if you have to ask, you probably won't understand the answer.



Welcome to BAUT, MrPibb. There's quite some history from the person posting this question, and that's what some of the other posters may be referring to. This may not be obvious to someone who just joined the board.


Thanks all for the welcome, and slang, I had some idea of that beforehand, and I do understand the frustration here, but on the other hand, I think I can identify with poster in trying to (sometimes vainly) visualize things where 1) one must entrench themselves in the math to gain even a subtle understanding, or 2) problems which lie well beyond the human(or my) capacity for understanding given our(mostly mine) current levels of knowledge. The only point to my thread drift is that the pursuit of knowledge, though a necessity for being well regulated and empirical exists, should not be discouraged in any form. Given the mathematical divergences that present themselves in our current theory, we may eventually find our understanding now to be as antiquated in its understanding as the "plum- pudding" atomic model. But I suppose that would indeed not be a suited discussion for a "mainstream" thread as it were.

Sorry for the rant, and I do hope for future conversations to be a little more pointed... cripes...:doh:

captain swoop
2009-Nov-24, 05:40 PM
MrPibb, welcome to BAUT, please take some time to read the rules for posting linked at the bottom of this post.

Q&A is for asking about and receiving answers on the Mainstream of Astronomy. 'Meta' discussion of the type you have posted should be confined to the Forum Introductions and Feedback forum

General note to all posters. Stick to answering questions. If you have a problem with a post or poster then report using the reporting triangle.
Attacks on other posters will result in Moderator Action

Jeff Root
2009-Nov-24, 05:56 PM
An answer to the original question which completely ignores general
relativity is that antigravity, if there is or were such a thing, would be
a repulsive gravitational force between matter. Similar to how opposite
electric charges attract and similar electric charges repel each other
by the electric force, similar gravitational masses attract each other,
and opposite gravitational masses would repel each other.

That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

-- Jeff, in Minneapolis

Fiery Phoenix
2009-Nov-24, 07:28 PM
SAn answer to the original question which completely ignores general
relativity is that antigravity, if there is or were such a thing, would be
a repulsive gravitational force between matter. imilar to how opposite
electric charges attract and similar electric charges repel each other
by the electric force, similar gravitational masses attract each other,
and opposite gravitational masses would repel each other.

That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

-- Jeff, in Minneapolis

Wouldn't repulsive gravity be more like a property of negative mass, though? Or did I just make that up?

DrRocket
2009-Nov-24, 08:41 PM
Wouldn't repulsive gravity be more like a property of negative mass, though? Or did I just make that up?

Negative mass would be even more weird.

Negative mass would accelerate to the left when you push it to the right.

cjameshuff
2009-Nov-24, 08:43 PM
Wouldn't repulsive gravity be more like a property of negative mass, though? Or did I just make that up?

It's a little more complex than just having negative mass. Just looking at Newtonian gravity:
F = G*m1*m2/r^2
A1 = F/m1 = G*m2/r^2
A2 = F/m2 = G*m1/r^2

A negative mass object would experience a force in the opposite direction...but would still accelerate in the same direction in a gravity field around a positive mass. It would however push either positive or negative masses away from it, and a mass and an "antimass" paired together would accelerate indefinitely.



That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

And I'll give my standard objection to this:
Gravity is actually proportional to *mass-energy*, not just mass.

The mass of a proton is not just that of its component quarks, it is in fact mostly due to the binding energy of those quarks. The binding energy of an antiproton should be the same, so if the quarks themselves had negative mass, we would measure a notable difference in mass between protons and antiprotons...the antiprotons as a whole still having positive mass.

If antiprotons actually have net negative mass-energy, that poses different problems. In pair production from a photon, the system would lose two protons worth of mass-energy. Proton-antiproton annihilation would add that amount of energy to the system. A container full of 1 kg of matter and 1 kg of antimatter would start with zero net gravitational effect from its contents, and would gain 2 kg as the two annihilated and it absorbed the resulting gamma radiation. You would have a closed system changing in mass-energy.

Also, if they have negative mass they should react in an opposite way to electromagnetic forces. Despite being electrically negative, anti-mass antiprotons should be attracted to negative charges. They should also bend the "wrong" way in magnetic fields. This sort of behavior would be quite difficult to miss. This should also allow you to do things like construct perpetual motion machines...

And in fact, measurements have been done, and they all point to an actual mass equal to that of protons. Jeff, I'm not sure why you reject the measurements that have been made.

tommac
2009-Nov-24, 08:46 PM
An answer to the original question which completely ignores general
relativity is that antigravity, if there is or were such a thing, would be
a repulsive gravitational force between matter. Similar to how opposite
electric charges attract and similar electric charges repel each other
by the electric force, similar gravitational masses attract each other,
and opposite gravitational masses would repel each other.

That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment wth anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.

-- Jeff, in Minneapolis

Where I really would like to ask is how would the expansion of the universe be different from this? I understand that mass isnt pushing everything apart but could empty space or dark energy have such an effect accelerating all matter away from it.

NOTE: I am not suggesting this ... just asking the question of how different would this be, as an attempt to understand the expansion of the universe as well as zero point energy.

tommac
2009-Nov-24, 08:47 PM
Negative mass would be even more weird.

Negative mass would accelerate to the left when you push it to the right.

where can I buy some of this stuff?

tommac
2009-Nov-24, 08:52 PM
It's a little more complex than just having negative mass. Just looking at Newtonian gravity:
F = G*m1*m2/r^2
A1 = F/m1 = G*m2/r^2
A2 = F/m2 = G*m1/r^2

A negative mass object would experience a force in the opposite direction...but would still accelerate in the same direction in a gravity field around a positive mass. It would however push either positive or negative masses away from it, and a mass and an "antimass" paired together would accelerate indefinitely.




And I'll give my standard objection to this:
Gravity is actually proportional to *mass-energy*, not just mass.

The mass of a proton is not just that of its component quarks, it is in fact mostly due to the binding energy of those quarks. The binding energy of an antiproton should be the same, so if the quarks themselves had negative mass, we would measure a notable difference in mass between protons and antiprotons...the antiprotons as a whole still having positive mass.

If antiprotons actually have net negative mass-energy, that poses different problems. In pair production from a photon, the system would lose two protons worth of mass-energy. Proton-antiproton annihilation would add that amount of energy to the system. A container full of 1 kg of matter and 1 kg of antimatter would start with zero net gravitational effect from its contents, and would gain 2 kg as the two annihilated and it absorbed the resulting gamma radiation. You would have a closed system changing in mass-energy.

Also, if they have negative mass they should react in an opposite way to electromagnetic forces. Despite being electrically negative, anti-mass antiprotons should be attracted to negative charges. They should also bend the "wrong" way in magnetic fields. This sort of behavior would be quite difficult to miss. This should also allow you to do things like construct perpetual motion machines...

And in fact, measurements have been done, and they all point to an actual mass equal to that of protons. Jeff, I'm not sure why you reject the measurements that have been made.

My thought that I am trying to rule out was that if empty space ( or maybe one of the following: cosomlogical constant, zero point energy, dark energy ) had an intrinsic tendency to accelerate mass away from it. And only when energy exists in quanties above the cosmological constant would this repulsive energy be negated as the sum of the curvature ( Ricci tensor) would be 0.

Please dont knock this into ATM as I am not going to defend that ... but I dont understand why this wouldnt work.

DrRocket
2009-Nov-24, 10:21 PM
My thought that I am trying to rule out was that if empty space ( or maybe one of the following: cosomlogical constant, zero point energy, dark energy ) had an intrinsic tendency to accelerate mass away from it. And only when energy exists in quanties above the cosmological constant would this repulsive energy be negated as the sum of the curvature ( Ricci tensor) would be 0.

Please dont knock this into ATM as I am not going to defend that ... but I dont understand why this wouldnt work.

It won't work because it makes no sense at all.

Nothing is "accelerating mass away from it". What is happening can be explained in terms of expansion of a space-like slice of space-time with distance measured from the metric inherited from the full space-time.

There is no such thing as the "sum of the curvature", although there is such a thing as Ricci curvature.

You are just throwing out words, with no apparent understanding of their meaning. It is not ATM. It is just word salad.

If you want to ask sensible questions or make meaningful conjectures you are simply going to have to learn some real physics, with real mathematics. Some references have been provided for you in earlier posts. No go read them.

WayneFrancis
2009-Nov-25, 05:09 AM
My thought that I am trying to rule out was that if empty space ( or maybe one of the following: cosomlogical constant, zero point energy, dark energy ) had an intrinsic tendency to accelerate mass away from it. And only when energy exists in quanties above the cosmological constant would this repulsive energy be negated as the sum of the curvature ( Ricci tensor) would be 0.

Please dont knock this into ATM as I am not going to defend that ... but I dont understand why this wouldnt work.

It doesn't work because if you take a look at the observations the observations don't match what you are suggesting.

Nothing is being moved in the universe when we talk about cosmic expansion. Relative to other objects everything is in the same position just the distances are the same. You can not think of it classically with a directional force unless we where the centre of the universe.

The analogy that dark energy = anti gravity falls down on this point. While they have some similar properties they are not the same.

Again anti-gravity should follow an inverse square law. Dark Energy has an effect that is observed to be linear in nature.

http://latex.codecogs.com/gif.latex?4\pi%20r^{2}%20!=%20rx%20\therefore%20An ti-gravity%20!=%20Dark%20Energy

aastrotech
2009-Nov-25, 09:08 AM
First we have to understand gravity itself. We don't. We can describe some of its effects and associations and they are fairly easy to understand as effects and associations but that's different from understanding gravity itself. Many people mistake understanding descriptions of effects and associations with understanding causes. Some of the primary effects and associations of gravity that can be described are that masses move through space and are attracted in their motion to each other. To understand gravity completely we have to have a complete understanding of all the elements from which the effects and associations emerge. A crucial instance is that we have to understand matter which has a primary association with mass. Our descriptions of matter (based as they are on our flawed and incomplete ability to observe it and interpret our observations of it) have fundamental flaws that result in theories that, even the best of which, are at present mutualy exclusive.

Since we don't fundamentaly understand matter we can't understand its motion and since a fundamental characteristic of motion is the space in which to move we don't understand space either.

Absent those fundamental understandings we have a way to go before understanding gravity let alone anti-gravity. If we did understand gravity well enough to either confirm anti-gravity or prove it impossible would not neccesarily stem from an absolutely consistant understanding of matter, motion and space. If we did have that we would know it (some of us anyway). At present we don't know enough to either strictly confirm or deny anti-gravity. At present we are absent conclusive evidence either way (though some with less strict standards of conclusive evidence would differ). But absence of evidence is not evidence of absence.

Kwalish Kid
2009-Nov-25, 01:25 PM
Well, I guess it must be hard for you to get to work. How do you manage to type using a computer, since it relies on so many principles that we do not understand?

tommac
2009-Nov-25, 09:20 PM
What is the difference between a ricci curvature in empty space vs the riccie curvature in nearly empty space? How can one describe the minimum amout of curvature via the terms of ricci curvature?






It won't work because it makes no sense at all.

Nothing is "accelerating mass away from it". What is happening can be explained in terms of expansion of a space-like slice of space-time with distance measured from the metric inherited from the full space-time.

There is no such thing as the "sum of the curvature", although there is such a thing as Ricci curvature.

You are just throwing out words, with no apparent understanding of their meaning. It is not ATM. It is just word salad.

If you want to ask sensible questions or make meaningful conjectures you are simply going to have to learn some real physics, with real mathematics. Some references have been provided for you in earlier posts. No go read them.

aastrotech
2009-Nov-25, 09:24 PM
Well, I guess it must be hard for you to get to work. How do you manage to type using a computer, since it relies on so many principles that we do not understand?

Because I understand the association of pressing keys with the effect of letters appearing on the screen. In the case of the typing I don't need to understand the cause. If I want to understand the cause well enough to do more than type I have to understand more than the association and the effect. It's kind of like understanding Bohr's atom is a good enough understanding of the atom as well as convienient to understand chemistry but insufficient to understand nuclear physics. Although nuclear physics is a more accurate description of the atom than Bohr's atom it is awkward to use for chemistry. Likewise nuclear physics specificly as applied under the Copenhagen interpretation (a convention) is convienient to understand nuclear physics but is insufficient to understand gravitational physics. Gravitational physics does not as yet exist as does nuclear physics. Our understanding of gravity completly falls apart under nuclear physics as applied under the Copenhagen interpretation.

tommac
2009-Nov-25, 09:25 PM
Nothing is being moved in the universe when we talk about cosmic expansion. Relative to other objects everything is in the same position just the distances are the same.

What is the difference of two things moving away from each other or the space between two objects are moving away from each other?

tommac
2009-Nov-25, 09:32 PM
Again anti-gravity should follow an inverse square law. Dark Energy has an effect that is observed to be linear in nature.

How do we observe this to be linear?

tommac
2009-Nov-25, 09:38 PM
Again anti-gravity should follow an inverse square law. Dark Energy has an effect that is observed to be linear in nature.


What if the "anti-gravity"/dark energy existed in the fabric of space-time regardless of if energy existed there or not.

What I am trying to ASK ... is that could it be inherent to space itself and not just grouped in empty space? If "anti-gravity" or dark matter existed everywhere then wouldnt its effects be linear?

Hornblower
2009-Nov-25, 10:05 PM
What if the "anti-gravity"/dark energy existed in the fabric of space-time regardless of if energy existed there or not.

What I am trying to ASK ... is that could it be inherent to space itself and not just grouped in empty space? If "anti-gravity" or dark matter existed everywhere then wouldnt its effects be linear?

Observations indicate a cosmic tendency toward accelerating expansion, for which physicists are using the placeholder term "dark energy" in the absence of an understanding of it. They choose not to call it "anti-gravity". I will leave it to those who are better informed than myself to explain why.

Gravity exists everywhere and is nonlinear.

Once again, you are asking a lot of far advanced questions in a field which is brutally unforgiving of missed prerequisites. I will readily admit that I am missing a lot of the prerequisites for understanding some of these items, despite having a bachelor's degree in physics. Einstein already had his Ph.D. and still needed another ten years of work on the mathematics to develop his GR theory. Present-day physicists with similar postdoctorate experience are scratching their heads in a quest to understand the things you are asking about. There are no quick and easy answers for those of us who are not immersed in their lines of work.

WayneFrancis
2009-Nov-25, 11:26 PM
What is the difference of two things moving away from each other or the space between two objects are moving away from each other?

The difference is the relative to the rest of the universe the objects are not approaching anything in the latter example but it would be in the first example.

And the space isn't "moving away from each other" the space is just increasing. A subtle but important distinction.

WayneFrancis
2009-Nov-25, 11:56 PM
How do we observe this to be linear?

Are you asking how we observe cosmic inflation to be linear?

Well...lets see....the rate of expansion is a linear equation of d(74km/mparsec/s)

so if something is 1 mega-parsec away it recedes at about 74km/s
if it is 2 mega-parsecs away it recedes at about 148km/s
if it is 3 mega-parsecs away it recedes at about 222km/s
if it is 4 mega-parsecs away it recedes at about 296km/s
if it is 5 mega-parsecs away it recedes at about 370km/s
if it is 6 mega-parsecs away it recedes at about 444km/s
see take the distance of the object in units of a megaparsec times that by 74km/s and you get the speed. That is what we call linear.

This is a lot different then
http://latex.codecogs.com/gif.latex?\frac{4\pi%20GM}{4\pi%20r^{2}}%20=%20\fr ac{GM}{r^{2}}
see the r2 under the GM...that means it it divided by ...the 2 slightly raised over the "r" indicates a square. So combine the the 2 and you get a inverse square law
So if I have an object like the Earth which is 5.9736 1024 kg this is the Min the equation above
G=6.67Nx10-11m2kg2
at 10,000km for r we get
6.67x5.9736x1013/100,000,000
or about
6.67x5.9736x105[sup]
39.843912x[sup]5

now double this to 20,000 and we get
6.67x5.9736x1013/400,000,000
see the numbers above the "/" don't change?!?! See that the number below the "/" has gone up by a factor of 4? This means the final number goes down by a factor of 4
at 30,000km the bottom number become 900,000,000
so it is lowered by a factor of 9
at 40,000km the bottom number becomes 1,600,000,000
so it is lowered by a factor of 16

I've said it before and I'll say it again. Spend a few minutes and look t the maths of what you are talking about. Your "gut feel" here about cosmic inflation being like anti-gravity fails with the first look at the maths.

This isn't even 9th grade maths here.

WayneFrancis
2009-Nov-26, 12:13 AM
What if the "anti-gravity"/dark energy existed in the fabric of space-time regardless of if energy existed there or not.

What I am trying to ASK ... is that could it be inherent to space itself and not just grouped in empty space? If "anti-gravity" or dark matter existed everywhere then wouldnt its effects be linear?

You are moving the goal post now. Dark matter's effect is linear. If you want to talk about the properties of what antimatter would be then we would expect, if it existed, that it would have the similar properties as gravity which is based on mass and follows an inverse square law.

short answer is "Yes, dark matter seems to be inherent to space and its effects are linear" Hurray, you understand the mainstream view on dark matter. Why then must you bring in terms like "anti-gravity"? This is like walking up to a biologist that is talking about a "cell" and say "hey isn't a 'cell' like a 'jail'?" Why start using terms that already have some other, but related, meaning to talk about something that already has a term defined for it?

Let us look at the 2, cosmic inflation and gravity
Cosmic inflation

Effect is linear
Effect seems to be increasing over time
Effect seems to be unaffected by mass
Effect does not move object but seems to create "more space"
Effect seems to be repulsive in nature


Suspected properties of anti-gravity based on gravity

Effect should follows an inverse square law
Effect should remain the same over time
Effect should be determined by mass
Effect should move object with relation to other objects.
Effect should be repulsive in nature


Only the last property is the same. If you want to call dark-energy anti-gravity then why not call magnetism gravity/anti-gravity. At least then there is more similar properties then dark-mater and anti-gravity.

Kwalish Kid
2009-Nov-26, 12:27 AM
How do we observe this to be linear?
We can measure the influence of dark energy on both expansion over time and over the entire geometry of the universe since the background radiation. We measure this based on the place in the Einstein field equation that we can fit dark energy, and this means that it is linear in effect. It also means that the influence of dark energy is through gravity, not against it.

tommac
2009-Nov-27, 03:57 PM
The difference is the relative to the rest of the universe the objects are not approaching anything in the latter example but it would be in the first example.

And the space isn't "moving away from each other" the space is just increasing. A subtle but important distinction.


I still dont get it. In an isolated env with 2 masses at one light year apart, what is the difference if the space in between the two masses increased to 2 ly or that the 2 masses moved apart to 2 ly away from each other?


Or are you saying that only in a more complex configuration would you be able to note this difference? How many points would we need to model this?

tommac
2009-Nov-27, 04:00 PM
Are you asking how we observe cosmic inflation to be linear?

Well...lets see....the rate of expansion is a linear equation of d(74km/mparsec/s).

Your first line answered that. However ... this is not true all over the universe correct? For example in gravitationally bound regions of space right?


My point is that if ALL of space ( including gravitationally bound parts of space) had an equal amount of repusion wouldnt the net effect be linear?

To some other point you made in a different email there would be no gradient. If there is no gradient wouldnt it be linear?

tommac
2009-Nov-27, 04:03 PM
Hurray, you understand the mainstream view on dark matter. Why then must you bring in terms like "anti-gravity"?

Um ... if I understood it why would I ask questions about it. I dont understand it so I am asking questions. I hope that is OK with you.

tommac
2009-Nov-27, 04:06 PM
Let us look at the 2, cosmic inflation and gravity
Cosmic inflation

Effect is linear
Effect seems to be increasing over time
Effect seems to be unaffected by mass
Effect does not move object but seems to create "more space"
Effect seems to be repulsive in nature

.

I have a few questions regarding these.

What do you mean by:


Effect seems to be unaffected by mass

I thought there is no expansion in gravitationally bound areas of space ...



Effect does not move object but seems to create "more space"


What is the evidence of this?

tommac
2009-Nov-27, 04:19 PM
It also means that the influence of dark energy is through gravity, not against it.

I have heard this a few times. Can you explain that as I thought its effect is repulsive?

Kwalish Kid
2009-Nov-27, 04:23 PM
I have heard this a few times. Can you explain that as I thought its effect is repulsive?
To understand it, all you have to do is go to your local library and pick up a basic text on cosmology published in the last six years, if not eight or nine. This will demonstrate the place of the cosmological constant in the Einstein Field Equation and will demonstrate the action of the cosmological constant in a revised Friedmann equation.

Felix Ibe
2009-Nov-27, 05:50 PM
since gravity is a downward force of attraction, hence anti-gravity will be an upward force of attraction. or a force that opposes the downward attraction of an object, thus making it to be attracted upward. but i still dont think that there is no anti-gravity.

Felix Ibe
2009-Nov-27, 05:55 PM
i fell anti-gravity happens in the space. am Bonquey. snd any other text 2 [e-mail address redacted by moderator]. bye......................

tommac
2009-Nov-27, 06:49 PM
so if something is 1 mega-parsec away it recedes at about 74km/s
if it is 2 mega-parsecs away it recedes at about 148km/s
if it is 3 mega-parsecs away it recedes at about 222km/s
if it is 4 mega-parsecs away it recedes at about 296km/s
if it is 5 mega-parsecs away it recedes at about 370km/s
if it is 6 mega-parsecs away it recedes at about 444km/s


From what I have been reading the further back in time we go the slower things were receeding. Wouldnt this example show constant expansion, rather than accelerated expansion?

antoniseb
2009-Nov-27, 06:57 PM
Are you asking how we observe cosmic inflation to be linear?...

No, that is not what he is asking. He is asking about Dark Energy, which is what we are calling the Acceleration of Cosmic Inflation that we've seen over the last six or seven billion years.

One reason we can be sure that Dark Energy is not "anti-gravity" is that anti-gravity would be an inverse-square repulsive force between two masses, which would simply emerge in the equations as a reduction in the total attractive force.

Also Dark Energy (by some papers) seems to be causing the greatest expansion in the voids (where there is little mass). It is hard to call this anti-gravity.

forrest noble
2009-Nov-27, 07:22 PM
Tommac,


Can someone please provide the mainstream definition of anti-gravity?

The closest entity (or hypothetical entities) that meets this description is probably Dark Energy: the widely accepted idea that something is pushing matter/ galaxies apart. Of course to get the best answer you'd have to define anti-gravity. A similar idea was Einstein's Cosmological Constant.

As to known sources of anti-gravity I would say that centrifugal pressures of a spinning body act against the forces of gravity for that body. EM radiation and atomic radiation in many cases act against the forces of gravity, and there are other examples.

As to a force that could assist a space craft separate from the above, I think that is still in the domain of science fiction or possibly basic research, where no accepted mainstream definition of anti-gravity exists.

tommac
2009-Nov-27, 07:28 PM
One reason we can be sure that Dark Energy is not "anti-gravity" is that anti-gravity would be an inverse-square repulsive force between two masses, which would simply emerge in the equations as a reduction in the total attractive force.
I can understand this however what confuses me is this gravitationally bound thing. The way I interpret that ( which has a good chance of being wrong ) is that at one point gravity is strong enough to overcome the expansive force. Then could we say that there is a distance where two objects could be where there would be no attractive or repulsive force winning the battle?
If that is the case then couldnt we say at any point between the two objects that there is a reduction in gravity exactly equal to the expansion of space? Would this then follow into Einstein's Cosmological Constant?
I appologize in advance if I am way off the mark on this. Also I am not proposing anything just wondering what is wrong with my understanding here.





Also Dark Energy (by some papers) seems to be causing the greatest expansion in the voids (where there is little mass). It is hard to call this anti-gravity.
Actually it is sort of exactly what I would expect, again please note that I am still in early learning stages for this. But I would think if there was a repulsive force that it would either tend to flow into a void to push itself away from mass/energy as it could, or it would be most evident in regions of space that are not gravitationally bound ( or in areas where gravity is not strong enough to cancel it out ).

if gravity pulls and creates things like galaxies and black holes ... anti gravity would repel things and create things like voids. The question would then become does anti-gravitational stuff or dark energy repel itself.

Sorry dont mean to dip into ATM here ... again just looking for where I am going off track.

tommac
2009-Nov-27, 07:31 PM
As to a force that could assist a space craft separate from the above, I think that is still in the domain of science fiction or possibly basic research, where no accepted mainstream definition of anti-gravity exists.

I am more looking to it in the sense of the exapnsion of the universe or zero point energy than I am as a fuel source.

forrest noble
2009-Nov-29, 09:01 PM
Tommac,

Re: Anti-gravity


I am more looking to it in the sense of the expansion of the universe or zero point energy than I am as a fuel source.


Assuming Dark Energy is a valid hypothesis, then its relationship with the ZPF does not seem to match present calculations.

quotes from this link: http://www.calphysics.org/zpe.html


Zero-point energy has the desired property of driving an accelerated expansion, and thus having the requisite properties of dark energy, but to an absurdly greater degree than required, i.e. 120 orders of magnitude.


.........the zero-point energy density is assumed to be constant: no matter how much the universe expands it does not become diluted, but instead more zero-point energy is assumed to be created out of nothing.

These are some of the hypothetical problems involved with the ZPF as the source of Dark Energy.

WayneFrancis
2009-Nov-30, 02:27 AM
I still dont get it. In an isolated env with 2 masses at one light year apart, what is the difference if the space in between the two masses increased to 2 ly or that the 2 masses moved apart to 2 ly away from each other?


Or are you saying that only in a more complex configuration would you be able to note this difference? How many points would we need to model this?

You can model this with 3 but the more point the more you can define what is happening with a higher degree of confidence.

The fact that we see almost everything receding away from us indicates one of 2 things.
1) we are in a very special place in the universe and everything is moving away from us
or
2) we are like every other place in the universe and space is being created at a certain rate increasing the distance between all objects

Option #1 has the problem that we see things receding at speeds >c which according to what we understand can not happen. Add to that the fact that there is no reason to think we are in a special place in the universe Option #2 is more likely.

WayneFrancis
2009-Nov-30, 02:32 AM
Your first line answered that. However ... this is not true all over the universe correct? For example in gravitationally bound regions of space right?


My point is that if ALL of space ( including gravitationally bound parts of space) had an equal amount of repusion wouldnt the net effect be linear?

To some other point you made in a different email there would be no gradient. If there is no gradient wouldnt it be linear?

no gradient isn't linear either. No gradient's equation would be f=0
not f=nd

At the largest scales the gravity of the universe is 0 if you think of it as a pull in a particular direction (note I'm not considering the great attractor here)

It is when you get down to smaller scales that we see the effects of mass being "clumpy" and thus gravity being "clumpy"

WayneFrancis
2009-Nov-30, 02:37 AM
Um ... if I understood it why would I ask questions about it. I dont understand it so I am asking questions. I hope that is OK with you.

Ok, but you explained it.

Your quote was


What I am trying to ASK ... is that could it be inherent to space itself and not just grouped in empty space? If "anti-gravity" or dark matter existed everywhere then wouldnt its effects be linear?

The bold bits describe dark energy.

I'll point out that I meant Dark Energy not dark matter also. Sorry for the confusion. Dark matter's effect is not linear.

Kwalish Kid
2009-Nov-30, 02:42 AM
Sorry dont mean to dip into ATM here ... again just looking for where I am going off track.
But have you looked to standard texts that explain this?

WayneFrancis
2009-Nov-30, 02:45 AM
I have a few questions regarding these.

What do you mean by:


Effect seems to be unaffected by mass

I thought there is no expansion in gravitationally bound areas of space ...


I've heard a few explainations
1) It might be a property of empty intergalactic space. Personally I don't like this explanation because it implies there is a a basic difference between the space between galaxies and the space between stars or planets or even just atoms.
2) It occurs everywhere but gravity swamps it on the smaller scales. This means that it has an effect but not one that is strong enough to push things apart at the smaller scale (this makes the most sense to me.
3) Some how matter retards the effect.





Effect does not move object but seems to create "more space"
What is the evidence of this?

well the fact that we observe everything moving away from us and if it was really moving then we have problems with things moving >c and we have the problem of why are we the only galaxy not "moving"

WayneFrancis
2009-Nov-30, 02:59 AM
From what I have been reading the further back in time we go the slower things were receeding. Wouldnt this example show constant expansion, rather than accelerated expansion?

Again it is a matter of scale.

at the 1-6 mega-parsec scale it is fairly constant. What we observe is the further back in time we go the slower the expansion rate.

It isn't simple math at that point. You can't look and say "Hey that point is 11 billion ly away from us and at 74km/Mpc that is 254,375km/s"

We've known for a long time that the Hubble constant is not constant over time. That it has been changing. The big surprise is that over the large scale it is increasing. Thus in 1 billion years we can expect it to be >74km/s/Mpc

This is why some call it the Hubble Variable. As depending on the "when" the value will be different.

WayneFrancis
2009-Nov-30, 03:02 AM
No, that is not what he is asking. He is asking about Dark Energy, which is what we are calling the Acceleration of Cosmic Inflation that we've seen over the last six or seven billion years.

One reason we can be sure that Dark Energy is not "anti-gravity" is that anti-gravity would be an inverse-square repulsive force between two masses, which would simply emerge in the equations as a reduction in the total attractive force.

Also Dark Energy (by some papers) seems to be causing the greatest expansion in the voids (where there is little mass). It is hard to call this anti-gravity.


Yup I see that but the fact that I carried on the DM term and didn't change it to DE ... I think tommac was still talking about DE.

As you say, better then I have been saying I think, the equations to describe DE are not the same as what we would expect to define Anti-gravity.

WayneFrancis
2009-Nov-30, 03:18 AM
I can understand this however what confuses me is this gravitationally bound thing. The way I interpret that ( which has a good chance of being wrong ) is that at one point gravity is strong enough to overcome the expansive force. Then could we say that there is a distance where two objects could be where there would be no attractive or repulsive force winning the battle?


Yes ... but this would be dependent on mass of the 2 objects and the distance involved. Since the scales here are so big it would be impossible to get something teetering on this knife edge. But in theory if you have 2 objects then you could place them at a point where they are not rotating around each other and that cosmic inflation would counteract the gravitational attraction of the 2 objects. If no other gravitational bodies interfered and the Hubble constant actually remained constant then they would sit there at the same distance for ever. But this is a thought experiment that could in practice never be performed.



If that is the case then couldnt we say at any point between the two objects that there is a reduction in gravity exactly equal to the expansion of space? Would this then follow into Einstein's Cosmological Constant?
I appologize in advance if I am way off the mark on this. Also I am not proposing anything just wondering what is wrong with my understanding here.


The amount that we are talking about is very low, below the error bars that we have for the gravitational constant. I've been through this with you before on other topics, also gravity related. If the effect is far below the existing error margin you have for a measurement then you can treat the effect as no effect at all.



Actually it is sort of exactly what I would expect, again please note that I am still in early learning stages for this. But I would think if there was a repulsive force that it would either tend to flow into a void to push itself away from mass/energy as it could, or it would be most evident in regions of space that are not gravitationally bound ( or in areas where gravity is not strong enough to cancel it out ).

if gravity pulls and creates things like galaxies and black holes ... anti gravity would repel things and create things like voids. The question would then become does anti-gravitational stuff or dark energy repel itself.

Sorry dont mean to dip into ATM here ... again just looking for where I am going off track.

Gravity can explain the voids. Are you wanting some other process to also explain the voids?

For example I put a bunch of ball barring in deep space and wait we can expect these ball bearings to start to clump together. The voids created don't need further explanation. Also the voids we see in intergalactic space aren't pushing things away from themselves as that would mean we would expect to see a bigger void "move" galaxies in the direction of smaller voids but we don't see that happening either.

astromark
2009-Nov-30, 07:11 AM
What do we know... ?
compared directly to
What we do not know... ?
All mass exhibits the qualities we call gravitational attraction force. There are no exceptions. When that said matter is so distant that its gravity has no perceptible measurable force. Then it would seem that the space it occupies would seem to expand taking this and these distant objects further from us... and everything else.
At this point I can not see a problem. What is it about this that is not understood ?
Taking attention to the small but, important fact. That we as interested parties to this subject ( gravity ) Do not know what it is or how it works... The fact that it does has led us to some conclusions that with knowledge may yet be proven as wrong... I call it science. Astronomy would seem to lean heavily in that direction.
My interpretation of this subject is just that, Mine. I have made a attempt to understand your questions. I draw the conclusion that a ATM idea is being tabled that I do not understand.
.

Jeff Root
2009-Nov-30, 08:01 AM
That antimatter actually has this anti-mass and anti-gravity property is
a pet hypothesis I have been nurturing since the mid-1970's. It should
be tested in an experiment with anti-hydrogen at CERN in about 2015 at
the earliest. It is unlikely to be a correct hypothesis, but one hopes.
And I'll give my standard objection to this:
Gravity is actually proportional to *mass-energy*, not just mass.
Yes, certainly. I said in the first sentence that I was completely
ignoring general relativity in my answer to the original question.
I continued to ignore GR when I described how my pet hypothesis
relates to that answer. That was for the sake of simplicity.



The mass of a proton is not just that of its component quarks, it is
in fact mostly due to the binding energy of those quarks. The binding
energy of an antiproton should be the same, so if the quarks themselves
had negative mass, we would measure a notable difference in mass
between protons and antiprotons...the antiprotons as a whole still
having positive mass.
It is certain that antiprotons have the same inertial mass as ordinary
protons. In order for antiprotons to have gravitational mass opposite
that of ordinary protons, their energy must have an effect opposite
to the effect of the same energy in ordinary protons.

In simple terms, I hypothesized that antiprotons have gravitational
mass opposite to that of ordinary protons, and inertial mass equal to
the absolute value of their gravitational mass.

But you made me realize that the simple idea of absolute value isn't
adequate. It appears to be necessary to describe gravitational mass
as the imaginary part of a complex value.

I now hypothesize that gravitational mass is +/-i times the inertial
mass, where, by convention, the gravitational mass of ordinary matter
is +i times the inertial mass, and the gravitational mass of
antimatter is -i times the inertial mass.

Where m is the inertial mass, gravitational mass of ordinary matter
is mg = mi, and gravitational mass of antimatter is mg = - mi,
by convention.

An antimatter scientist in an antimatter world would find that his
inertial and gravitational masses are indistinguishable, just as we
find our inertial and gravitational masses indistinguishable.

But, I hypothesize, he would find-- just as we would-- that his
matter and our matter have opposite gravitational masses. One has
a value of +mi, and the other has a value of -mi.



If antiprotons actually have net negative mass-energy, that poses
different problems. In pair production from a photon, the system would
lose two protons worth of mass-energy.
That clearly doesn't happen.

My hypothesis is that energy in antimatter has opposite gravitational
effect to the same energy in ordinary matter. No negative mass-energy
is involved.



Proton-antiproton annihilation would add that amount of energy to the
system. A container full of 1 kg of matter and 1 kg of antimatter would
start with zero net gravitational effect from its contents, and would
gain 2 kg as the two annihilated and it absorbed the resulting gamma
radiation. You would have a closed system changing in mass-energy.
My hypothesis is that one part of this is correct: The gravitational
effects of equal quantities of matter and antimatter cancel each other.
If they are separated from each other, their gravitational effects
would be observed to be opposite. If they come together and annihiate
each other, and the products of the annihilation remain together in
one place, the gravitational effects would continue to cancel. If the
products separate into ordinary matter and antimatter components, the
ordinary component would have ordinary gravity and the antimatter
component would have antigravity.

I realized quite a few years ago that in order for antimatter to have
antigravity would require that antiphotons be different from ordinary
photons. We see ordinary gravitational lensing of ordinary photons
by ordinary gravity. So antigravity would have to cause a different
lensing of ordinary photons: faint radial lines instead of bright
circumferential arcs. The same applies to antiphotons in ordinary
gravity.



Also, if they have negative mass they should react in an opposite
way to electromagnetic forces. Despite being electrically negative,
anti-mass antiprotons should be attracted to negative charges. They
should also bend the "wrong" way in magnetic fields.
None of that applies. My hypothesis is a reversal of gravitational
mass, not inertial mass.



This sort of behavior would be quite difficult to miss.
No kidding. It is not what my hypothesis predicts.



This should also allow you to do things like construct perpetual
motion machines...

And in fact, measurements have been done, and they all point to an
actual mass equal to that of protons. Jeff, I'm not sure why you
reject the measurements that have been made.
I am not rejecting any measurements. These objections apply to
differences in inertial mass, energy, or electromagnetic properties,
which are not consequences of my hypothesis.

-- Jeff, in Minneapolis

tommac
2009-Nov-30, 04:12 PM
I understand this, I think, but again my question is what is the difference between space expanding between all of the objects and the objects moving away from each other. For example using the rasin bread example as the bread rises ... all of the raisins move away from each other is this the same as space increasing between each of the raisins? To me it is the same thing.

Is the only differenciation, that things are moving away from us at faster than the speed of light which should be illegal because of relativity?


You can model this with 3 but the more point the more you can define what is happening with a higher degree of confidence.

The fact that we see almost everything receding away from us indicates one of 2 things.
1) we are in a very special place in the universe and everything is moving away from us
or
2) we are like every other place in the universe and space is being created at a certain rate increasing the distance between all objects

Option #1 has the problem that we see things receding at speeds >c which according to what we understand can not happen. Add to that the fact that there is no reason to think we are in a special place in the universe Option #2 is more likely.

tommac
2009-Nov-30, 04:15 PM
no gradient isn't linear either. No gradient's equation would be f=0
not f=nd

At the largest scales the gravity of the universe is 0 if you think of it as a pull in a particular direction (note I'm not considering the great attractor here)

It is when you get down to smaller scales that we see the effects of mass being "clumpy" and thus gravity being "clumpy"


Sorry, still dont get it. I understand that the universe is just expanding ... not in any one direction. However what I am talking about is that if there is a repulsive force at every point of space time, its effect would be linear throughout the universe.

Confused about your answer ... can you please reword?

tommac
2009-Nov-30, 04:17 PM
But have you looked to standard texts that explain this?
Of course. Have I read everybook ever written ... no .... but I have read quite a few.

tommac
2009-Nov-30, 04:28 PM
I've heard a few explainations
1) It might be a property of empty intergalactic space. Personally I don't like this explanation because it implies there is a a basic difference between the space between galaxies and the space between stars or planets or even just atoms.
2) It occurs everywhere but gravity swamps it on the smaller scales. This means that it has an effect but not one that is strong enough to push things apart at the smaller scale (this makes the most sense to me.
3) Some how matter retards the effect.


Wow ... it looks like we are in agreement. #2 is also the one that makes the most sense to me. #1 can make sense to me if there are anti-gravitational particles ( all trying to push as far away from everything else as possible ). But I like #2 more and am trying to think it through.



well the fact that we observe everything moving away from us and if it was really moving then we have problems with things moving >c and we have the problem of why are we the only galaxy not "moving"

I am not sure why you would think that it would mean that we the only galaxy not "moving"? if everything is moving away from us ... then wouldnt that mean that we are moving away from everything else? What is movement, movement is relative. if we have 3 isolated objects, if 2 objects are moving away from themselves and away from the third object, then it depends on which object is the observer as to which objects are moving away from what? As an observer it is usually easier to think of things moving away or towards us ... but as you can see that regardless of which object we choose as the observer the other two objects are moving away from "the observer" and away from the other two.

Now about the > C issue, I am not sure about that. However I really dont understand the magically appearing space. Is it topological? Is it relativistic?

If space itself has a repulsive characteristic ... could it also repell lght? If so what would that be like? Light always travels at c ... but if it would be repelled ( by anti-gravity ) wouldnt it red-shift? Or would it all net out? Getting a little off track here but just want you to know where my questions are coming from.

tommac
2009-Nov-30, 04:33 PM
Again it is a matter of scale.

at the 1-6 mega-parsec scale it is fairly constant. What we observe is the further back in time we go the slower the expansion rate.

It isn't simple math at that point. You can't look and say "Hey that point is 11 billion ly away from us and at 74km/Mpc that is 254,375km/s"

We've known for a long time that the Hubble constant is not constant over time. That it has been changing. The big surprise is that over the large scale it is increasing. Thus in 1 billion years we can expect it to be >74km/s/Mpc

This is why some call it the Hubble Variable. As depending on the "when" the value will be different.


Now you have me totally confused. So you are saying only 1-6 are at 74 but 7-11 are slower ... which is kind of what I thought. The rate of expansion is not d(74km/mparsec/s) but a more complex calculation. That needs to figure in gravity and expansion and time and states of the universe in the past.



Are you asking how we observe cosmic inflation to be linear?

Well...lets see....the rate of expansion is a linear equation of d(74km/mparsec/s)

so if something is 1 mega-parsec away it recedes at about 74km/s
if it is 2 mega-parsecs away it recedes at about 148km/s
if it is 3 mega-parsecs away it recedes at about 222km/s
if it is 4 mega-parsecs away it recedes at about 296km/s
if it is 5 mega-parsecs away it recedes at about 370km/s
if it is 6 mega-parsecs away it recedes at about 444km/s
see take the distance of the object in units of a megaparsec times that by 74km/s and you get the speed. That is what we call linear.

tommac
2009-Nov-30, 04:40 PM
Gravity can explain the voids. Are you wanting some other process to also explain the voids?


So then are you claiming that the expansion of space is really little more than the clumping of ball bearings? From what I understand, which isnt much, is that there is more to it than that. In fact the expansion of space is greatest in the voids. if that is the case then the voids themselves have some repulsive force or that the gravitational pull on the rest of the universe is pulling stuff away from the voids in all directions. Can you please go into a little more detail?

Kwalish Kid
2009-Nov-30, 04:42 PM
Of course. Have I read everybook ever written ... no .... but I have read quite a few.
So you are familiar with the role of the cosmological constant in the Friedmann equation?

tommac
2009-Nov-30, 04:52 PM
So you are familiar with the role of the cosmological constant in the Friedmann equation?

Yes. I am familiar. I dont fully understand the math but I think I have my head wrapped around the idea. I think it was initially put there because if it wasnt there the universe would always collapse due to gravity. Is that wrong? So it was added as an inherint cost of doing business with the universe.

Kwalish Kid
2009-Nov-30, 05:20 PM
The cosmological constant is the representative of dark energy. The Friedmann equation represents the action of gravity in the large scale of a roughly homogeneous and isotropic universe.

This is how a "repulsive force" can act through gravity.

forrest noble
2009-Nov-30, 06:43 PM
Tommac,

concerning the idea of an expanding universe or accelerated expansion:


.......my question is what is the difference between space expanding between all of the objects and the objects moving away from each other. For example using the raisin bread example as the bread rises ... all of the raisins move away from each other is this the same as space increasing between each of the raisins? To me it is the same thing.

(bold added)

Using the "objects-moving-away-from-each-other" explanation one would have to explain what property of matter could cause this to occur. To the contrary, everything we observe seems to indicate that in time objects tend to move toward each other, hence gravity.

When using the space-expanding-between-all-of-the-objects" (matter) explanation one could propose that over time space expands. This does not seem to violate any presently known principles.


Is the only differentiation, that things are moving away from us at faster than the speed of light which should be illegal because of relativity?

According to the Theory of Special Relativity, and LET as well, each thing (matter) can be considered stationary when evaluating relative motion. Just based upon logic alone we might realize that to us distant galaxies seem to be moving away at speeds faster than the speed of light for redshifts greater than 1, but if there was an observer in those distant galaxies, to "him" we would be the ones moving away at speeds faster than the speed of light.

tommac
2009-Nov-30, 08:39 PM
Thanks ... I understand / agree with all of this ...

But when two items attract each other do we consider that the space between them is contracting? I usually hear this stated that the two objects are attracting each other or that they are moving towards each other.



Tommac,

concerning the idea of an expanding universe or accelerated expansion:



(bold added)

Using the "objects-moving-away-from-each-other" explanation one would have to explain what property of matter could cause this to occur. To the contrary, everything we observe seems to indicate that in time objects tend to move toward each other, hence gravity.

When using the space-expanding-between-all-of-the-objects" (matter) explanation one could propose that over time space expands. This does not seem to violate any presently known principles.



According to the Theory of Special Relativity, and LET as well, each thing (matter) can be considered stationary when evaluating relative motion. Just based upon logic alone we might realize that to us distant galaxies seem to be moving away at speeds faster than the speed of light for redshifts greater than 1, but if there was an observer in those distant galaxies, to "him" we would be the ones moving away at speeds faster than the speed of light.

forrest noble
2009-Nov-30, 10:13 PM
tommac,


when two items attract each other do we consider that the space between them is contracting?


According to the standard model of gravity, General Relativity, the space surrounding matter "warps" but no "contraction" resulting in less space would accordingly result. Any surrounding matter accordingly would follow the path of these "lines" of warped space inward resulting in less space/ distance as time passes.

Here is one description concerning General Relativity, which is a more widely accepted gravitational theory than any other including Quantum Gravity (which is still in development): http://www.astronomynotes.com/relativity/s4.htm


I usually hear this stated that the two objects are attracting each other ......

The attraction idea is mostly Newtonian but even some Quantum Gravity hypothesis involve gravitons (theoretical particles) originating from the direction of the Earth (for example) which transfer a force to matter in the vicinity "pulling" (attracting) the matter inward, or gravity waves of some kind somehow pulling matter inward. Gravitational Attraction is common wording in textbooks of secondary education (before college). It's also often used in collegiate texts since the phrasing is much simpler than saying that matter "is moving into warped space" surrounding other matter or something similar. Even NASA uses this wording of "attraction," at least sometimes as I recall, concerning their publicly distributed information.

concerning gravitational influences of two objects:


..........or that they are moving towards each other.

As you probably know, matter moving toward each other does not always mean gravitational attraction. Relative motion can result in a similar reduction of space between matter but with a constant speed until gravitational influences accelerate and/ or "bend" the motion.

tommac
2009-Nov-30, 10:45 PM
Thanks ... I understand this ... however I think my point was missed.

When we think of gravity, when I jump up in the air and return to the ground,
we can say that i have moved away from the earth and then I move
back towards the earth. We usually dont say that I moved away from the earth and then the space between the earth and myself warped. Although it could be argued that it is the same thing.

For expanding space, things are moving away from us that is the same as saying the space between two objects is expanding right?

Now, can one argue, that no form of curviture could result in more space, rather than less space? If so isnt that where the Ricci Tensor comes in?
Can space be warped in a way where space expands? Would we need to use imaginary numbers to accomplish that? Or can that be natural for a tensor?

The other question I have here, is: What if space-time was naturally slightly curved but in the deep voids of space it becomes just about straight, providign an illusion of things moving further apart. Is that possible?

Sorry about the wording on all of this.




tommac,



According to the standard model of gravity, General Relativity, the space surrounding matter "warps" but no "contraction" resulting in less space would accordingly result. Any surrounding matter accordingly would follow the path of these "lines" of warped space inward resulting in less space/ distance as time passes.

Here is one description concerning General Relativity, which is a more widely accepted gravitational theory than any other including Quantum Gravity (which is still in development): http://www.astronomynotes.com/relativity/s4.htm



The attraction idea is mostly Newtonian but even some Quantum Gravity hypothesis involve gravitons (theoretical particles) originating from the direction of the Earth (for example) which transfer a force to matter in the vicinity "pulling" (attracting) the matter inward, or gravity waves of some kind somehow pulling matter inward. Gravitational Attraction is common wording in textbooks of secondary education (before college). It's also often used in collegiate texts since the phrasing is much simpler than saying that matter "is moving into warped space" surrounding other matter or something similar. Even NASA uses this wording of "attraction," at least sometimes as I recall, concerning their publicly distributed information.

concerning gravitational influences of two objects:



As you probably know, matter moving toward each other does not always mean gravitational attraction. Relative motion can result in a similar reduction of space between matter but with a constant speed until gravitational influences accelerate and/ or "bend" the motion.

WayneFrancis
2009-Nov-30, 11:47 PM
I understand this, I think, but again my question is what is the difference between space expanding between all of the objects and the objects moving away from each other. For example using the rasin bread example as the bread rises ... all of the raisins move away from each other is this the same as space increasing between each of the raisins? To me it is the same thing.

Is the only differenciation, that things are moving away from us at faster than the speed of light which should be illegal because of relativity?

I guess I'm trying to emphasise that when space expands at >c that no 2 objects will approach each other at a speed >c

If I take an object and just "move" it then it will get further away from some objects but because the universe is full of objects it will also get closer to others. The rate at which is moves towards or away from any object is a function of the angle between the 2 objects and the vector of the motion.

In cosmic inflation where all objects have the same angle there is no 2 objects that ever get closer due to cosmic inflation thus there is nothing illegal as far as relativity goes. Simply put no information is travelling through space faster then c. In fact as far as cosmic inflation goes no information is actually moving through space due to cosmic inflation.

It is a subtle but very important distinction.

WayneFrancis
2009-Dec-01, 12:33 AM
Sorry, still dont get it. I understand that the universe is just expanding ... not in any one direction. However what I am talking about is that if there is a repulsive force at every point of space time, its effect would be linear throughout the universe.

Confused about your answer ... can you please reword?

The gradient issue was in reference to your other thread talking about gravitational potential.

I'll use an analogy NorthernBoy brought up in another thread.

If you talk about gravitational potential in the early universe or dark energy's potential then it is a bit like talking about the energy potential of the ocean pressure on the bottom of the ocean. Sure it is all around you but you are not going to be able to extract it.

The gradient issue came up from your comment


To some other point you made in a different email there would be no gradient. If there is no gradient wouldnt it be linear?

So you are mixing another thread with this one and the 2 are about different things.

1 is talking about gravity where there is no gradient and this one is about dark energy which we've said over and over does NOT work like gravity or anti gravity. Gravity moves objects THROUGH space and works on an inverse square law, and where there is no gradient this amounts to 0, and dark energy creates space and is linear.

You keep trying to tie Dark energy into gravity. Its like calling a rip tide "anti swimming" because if you are swimming against it then to changes your movement through the ocean and even that analogy breaks down very quickly so don't read to much into it.

WayneFrancis
2009-Dec-01, 12:50 AM
...
I am not sure why you would think that it would mean that we the only galaxy not "moving"? if everything is moving away from us ... then wouldnt that mean that we are moving away from everything else? What is movement, movement is relative. if we have 3 isolated objects, if 2 objects are moving away from themselves and away from the third object, then it depends on which object is the observer as to which objects are moving away from what? As an observer it is usually easier to think of things moving away or towards us ... but as you can see that regardless of which object we choose as the observer the other two objects are moving away from "the observer" and away from the other two.


Again I'm steering clear of the word "Move" because of its over all concept. Take a chess board and "move" a piece. It will get "closer" to other pieces while getting "further" from others.

Now say that chess board was a piece of latex and the pieces were tacked to a single points on the chess board and you stretched the chess board in all directions at the same time. On the chess boards NONE of the pieces have "moved" the only "movement" is in a higher perspective from outside the chess board.

I'm steering clear of the "Move" specifically because I don't want people to think that anything is actually moving closer to something else in regards to the expansion.



Now about the > C issue, I am not sure about that. However I really dont understand the magically appearing space. Is it topological? Is it relativistic?


I would not say it is topological because that implies a geometric change in my mind. Cosmic inflation doesn't change any of the angles. Just the distances. Smaller triangles just become larger ones so I guess I would call it relative but not relativistic as relativistic implies a bit more then I'm willing to assign to the phenomena without giving it more thought.

I'd also say you should take out the "magically" in the quote above. It adds a connotation that isn't needed. Unless you call anything "Magic" that you don't yet know about. Do you understand French? Do you think there is anything magical about French language?



If space itself has a repulsive characteristic ... could it also repell lght? If so what would that be like? Light always travels at c ... but if it would be repelled ( by anti-gravity ) wouldnt it red-shift? Or would it all net out? Getting a little off track here but just want you to know where my questions are coming from.

Can it repel light? No but it can stretch out the light.
Again stop equating Dark Energy with Anti-Gravity. Gravity is an effect that "moves" stuff through space. Dark energy is something that "creates" space. 2 different effects.

That said yes if you had an effect that was "anti gravity" then I would expect light to be red shifted as it tries to climb the gravity hill so to speak. But again this effect is different then cosmic inflation/red shift.

WayneFrancis
2009-Dec-01, 12:58 AM
Now you have me totally confused. So you are saying only 1-6 are at 74 but 7-11 are slower ... which is kind of what I thought. The rate of expansion is not d(74km/mparsec/s) but a more complex calculation. That needs to figure in gravity and expansion and time and states of the universe in the past.

Don't read to much into my numbers but you've got the basics right. The cosmic inflation is not a constant rate when you look back in time. What we do expect is the following.

At any average point in the universe the Hubble constant will be the same as any other point in the universe for given that the time since the big bang was the same.

So Say we have 2 points A & B that are 10 billion light years apart.

If A looks at point B and measures B's hubble constant at n then they would expect that 10 billion years ago that their Hubble constant (point A) would have also been n

So yes it isn't as easy as measuring the distance and plugging a number into a formula.

I can't find one but someone else might have a chart of the Hubble Constant over time as we understand it right now.

WayneFrancis
2009-Dec-01, 01:27 AM
So then are you claiming that the expansion of space is really little more than the clumping of ball bearings? From what I understand, which isnt much, is that there is more to it than that. In fact the expansion of space is greatest in the voids. if that is the case then the voids themselves have some repulsive force or that the gravitational pull on the rest of the universe is pulling stuff away from the voids in all directions. Can you please go into a little more detail?

No, what I said is the voids can be explained by gravity clumping up the matter into galaxies.

The greater voids create more space because there is more space in them. But if I have 2 void in line that are half the size of 1 big void then the 2 voids will create just as much space as the 1 big void. Per unit of space the rate is the same. I'm very careful with my selection of words because saying something like

In fact the expansion of space is greatest in the voids.
can easily be read as "the rate at which space is created is greatest dependent on the size of the void"

The rate is the same, right now that is 74km/s/Mpc regardless of where you are at as long as you are at ~14.5by from the big bang in time, and you are in typical location in the universe.

So pick any point in the universe you want, please don't pick the EH of a black hole.
If your time since the big bang is roughly 14.5by then your Hubble constant should be ~74km/s/Mpc

WayneFrancis
2009-Dec-01, 01:30 AM
Thanks ... I understand / agree with all of this ...

But when two items attract each other do we consider that the space between them is contracting? I usually hear this stated that the two objects are attracting each other or that they are moving towards each other.

NO!!!!


Gravity/Anti-gravity and Dark energy are NOT the same type of creature. Wipe your conception from your brain. Say it over and over.

Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.

Come back in a couple of days.

WayneFrancis
2009-Dec-01, 01:41 AM
Thanks ... I understand this ... however I think my point was missed.

When we think of gravity, when I jump up in the air and return to the ground,
we can say that i have moved away from the earth and then I move
back towards the earth. We usually dont say that I moved away from the earth and then the space between the earth and myself warped. Although it could be argued that it is the same thing.

For expanding space, things are moving away from us that is the same as saying the space between two objects is expanding right?

Now, can one argue, that no form of curviture could result in more space, rather than less space? If so isnt that where the Ricci Tensor comes in?
Can space be warped in a way where space expands? Would we need to use imaginary numbers to accomplish that? Or can that be natural for a tensor?

The other question I have here, is: What if space-time was naturally slightly curved but in the deep voids of space it becomes just about straight, providign an illusion of things moving further apart. Is that possible?

Sorry about the wording on all of this.

If you want to talk about warping of space. Gravity warps space dark energy does not. So we have yet another property of gravity that is not present in dark energy.

When you "jump" you are not creating space between you and the Earth. You are "climbing" out of a gravity well. The energy you use to "climb" out of the Earth's gravity well become your "gravitational potential" when you fall back to Earth you liberate that potential.

Now lets look at cosmic inflation. While 2 objects separation gets larger the gravitational potential does not get larger because we can't turn this inflation off.

It is like those air tunnels where you can "sky dive" in a room. You are in a constant free fall but the air is constantly pushing you up. All that energy that is used to push you off the floor isn't accumulated.

If by some form of magic the dark energy turned off then yes there would essentially be a lot of gravitational potential that could then be liberated. But we have no reason to think this would happen any more then we should think that gravity will just turn off one day destroying all the gravitational potential in the universe.

Kwalish Kid
2009-Dec-01, 01:48 AM
If you want to talk about warping of space. Gravity warps space dark energy does not. So we have yet another property of gravity that is not present in dark energy.
What are you talking about? Every serious scientific paper that shows any measurement of dark energy does so by detecting the way that dark energy changes spacetime through gravity.

forrest noble
2009-Dec-01, 02:32 AM
tommac,


When we think of gravity, when I jump up in the air and return to the ground, we can say that i have moved away from the earth and then I move back towards the earth. We usually don't say that I moved away from the earth and then the space between the earth and myself warped. Although it could be argued that it is the same thing.

Of course the common wordings we use for the effects of gravity are unrelated to the Theory of General Relativity (GR) as I mentioned before. This common-use wording is usually related to Newtonian gravity (the pull of gravity). The wording for GR, I think, would be something like this:
as you (mass) move parallel to the "lines of warp" you are directed by your momentum relative to the gravitational body (the Earth for example) and the warp lines produced by gravity. As you move perpendicular to those lines you will reach a height according to your upward momentum as you decelerate (from a single push). If you are overcome by gravity, you will reverse your momentum and accelerate toward the mass at a rate according to the mass and your distance away from the center of mass which together determine the warp lines that you will encounter and your resultant rate of acceleration toward the mass. If your motion combines the two relative motions then both factors/ wordings would be involved.


For expanding space, things are moving away from us; that is the same as saying the space between two objects is expanding right?


No, it's not the same. According to the standard model of cosmology which incorporates the theory of the expansion of space, you could only say that the motion away from us is based upon the expansion of space if the relative motion is equivalent to the expansion rate of space according to theory (like the Hubble Constant rate or a constant rate plus an acceleration factor.)

Now, can one argue, that no form of curvature could result in more space, rather than less space?....

Einstein's Cosmological equations plus his Cosmological Constant could, according to what I have read concerning an expanding universe solution, result in an accelerated expansion of space solution, i.e. more space rather than less space which hypothetically could relate to the curvature of space.

re: possible curvatures of space


.....If so isn't that where the Ricci Tensor comes in?

The Ricci Tensors are Minkowsky (four dimensional which include Cartesian coordinates plus time) vectors which when combined calculate the real-motion vectors of an object and are related to its predicted path/ motion and generally unrelated to changes in the expansion of space.


Can space be warped in a way where space expands?

I suppose it could but this would not be according to Einstein's Cosmological Equations without the Cosmological Constant.


Would we need to use imaginary numbers to accomplish that? Or can that be natural for a tensor? No, it's the same formulation with one Constant added.


The other question I have here, is: What if space-time was naturally slightly curved but in the deep voids of space it becomes just about straight, providing an illusion of things moving further apart. Is that possible?

I think this, or something similar, could be an (ATM) hypothesis concerning the cause of redshifts, whereby no real expansion of the universe is involved -- or that expansion would have a different meaning, or a hypothetical explanation of the appearance of accelerated expansion. I think it would be very difficult to defend, however, since I know of no evidence to support it other than the galactic redshifts, and the proposed accelerated expansion, maybe the only two things that it would be attempting to explain.

Did I understand your questions properly?

tommac
2009-Dec-01, 04:55 PM
I know that dark matter and dark energy are not the same. Dark matter is what holds universes together and dark energy is like the cosmological constant or the thing we use to explain why the universe is expanding.

What I am questioning has to do with neither of them. It is just the terminology that I am having problems with.

The question is simple. What is expanding space, and how does expanding space differ from objects moving away from each other.


The point that I was trying to make is that when we look at gravity ( didnt say anything about either dark matter or dark energy ) we dont usually say that space is contracting we say that two objects are moving towards each other, although arguably you could say that the space between the two objects is warped.

For the expansion of space however, I am confused why we can only say that space is expanding and we can not say that all objects ( not gravitationally bound ) are moving away from each other .... is there a difference?



NO!!!!


Gravity/Anti-gravity and Dark energy are NOT the same type of creature. Wipe your conception from your brain. Say it over and over.

Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.
Gravity/Anti-gravity and Dark energy are NOT the same type of creature.

Come back in a couple of days.

tommac
2009-Dec-01, 04:57 PM
If you want to talk about warping of space. Gravity warps space dark energy does not. So we have yet another property of gravity that is not present in dark energy.

I thought that only when Z=1 that we have unwarped space. Are you saying that the expansion of space is not topological? If it has to do with the topology, then wouldnt it be warped ( in the opposite way of gravity)? Again I am confused about this but not clear on the point that you are making.

tommac
2009-Dec-01, 05:06 PM
Awesome post. Thank you for taking the time! This really helped. Esp. regarding the Ricci Tensor.

So as a follow up question ... what would a Ricci tensor ( or other tensor ) look like that would force "lines of warp" away from a point ( just talking mathmatical here ) ? Could that be shown vs a Ricci tensor say for a BH or star or something? I am getting the idea of the Ricci tensor but would like to see it in action if that is possible. Hope I am not asking too much.


tommac,



Of course the common wordings we use for the effects of gravity are unrelated to the Theory of General Relativity (GR) as I mentioned before. This common-use wording is usually related to Newtonian gravity (the pull of gravity). The wording for GR, I think, would be something like this:
as you (mass) move parallel to the "lines of warp" you are directed by your momentum relative to the gravitational body (the Earth for example) and the warp lines produced by gravity. As you move perpendicular to those lines you will reach a height according to your upward momentum as you decelerate (from a single push). If you are overcome be gravity, you will reverse your momentum and accelerate toward the mass at a rate according to the mass and your distance away from the center of mass which together determine the warp lines that you will encounter and your resultant rate of acceleration toward the mass. If your motion combines the two relative motions then both factors/ wordings would be involved.



No, it's not the same. According to the standard model of cosmology which incorporates the theory of the expansion of space, you could only say that the motion away from us is based upon the expansion of space if the relative motion is equivalent to the expansion rate of space according to theory (like the Hubble Constant rate or a constant rate plus an acceleration factor.)


Einstein's Cosmological equations plus his Cosmological Constant could, according to what I have read concerning an expanding universe solution, result in an accelerated expansion of space solution, i.e. more space rather than less space which hypothetically could relate to the curvature of space.

re: possible curvatures of space



The Ricci Tensors are Minkowisky (four dimensional which include Cartesian coordinates plus time) vectors which when combined calculate the real-motion vectors of an object and are related to its predicted path/ motion and generally unrelated to changes in the expansion of space.



I suppose it could but this would not be according to Einstein's Cosmological Equations without the Cosmological Constant.

No, it's the same formulation with one Constant added.



I think this, or something similar, could be an (ATM) hypothesis concerning the cause of redshifts, whereby no real expansion of the universe is involved -- or that expansion would have a different meaning, or a hypothetical explanation of the appearance of accelerated expansion. I think it would be very difficult to defend, however, since I know of no evidence to support it other than the galactic redshifts, and the proposed accelerated expansion, maybe the only two things that it would be attempting to explain.

Did I understand your questions properly?

forrest noble
2009-Dec-01, 07:28 PM
tommac,


So as a follow up question ... what would a Ricci tensor ( or other tensor ) look like that would force "lines of warp" away from a point ( just talking mathmatical here )?

"Lines of warp" are more an analogy than a description of the mathematical results. GR equations produce non-linear results. Because it includes the "dimension of time" it can trace the path of gravitational influence that generally have curved geometric forms. It is the "increased spacing" between possible paths (based upon the relative location and momentum) that might be described as indications of warp surrounding matter as pictorialized toward the bottom of this link. http://www.astronomynotes.com/relativity/s4.htm

Your wording "force lines of warp away from a point" may not be the best way to describe the analogy but I don't think wording in general can adequately describe mathematical increments of change as well as it can be pictorialized, which is still an analogy.


Could that be shown vs a Ricci tensor say for a BH or star or something? I am getting the idea of the Ricci tensor but would like to see it in action if that is possible.

The equations of GR are called field equations (http://www.google.com/search?hl=en&source=hp&q=define%3A+field+equations&btnG=Google+Search&aq=f&oq=&aqi=) which are a set of 10 non-linear partial differential equations of tensor calculus which have to be solved for the "metric tensor." Its non-linear equations are very difficult to solve without doing "suitable" approximations in almost all cases. However today using large computers there have been cases where "exact solutions" have been made.

definitions: http://www.hitxp.com/articles/science-technology/general-relativity-field-equations-simplified/

If you would graph out the results of GR on a three dimensional pictograph based upon the relative location and momentum of possible paths of orbiting matter, you would end up with a picture something like a three dimensional version (the path based upon elapsed time and equal spacing to start with) of the pictorialized version shown in the top link, concerning the warping of space. There would be no difference between the Earth, a star, or a BH when pictorialized excepting for the increasing "distances between lines" as matter gets closer to the gravity source of larger gravitational influences.

I know you hoped for more based upon your quote : "...would like to see it in action", but that was the best explanation that I could give regarding a mainstream explanation of the results/ effects of GR and the idea of the warping of space.

tommac
2009-Dec-01, 09:41 PM
So you are mixing another thread with this one and the 2 are about different things.



I am mixing on purpose. My point or rather question was that if anti-gravity (dark energy) was distributed evenly everywhere, then would there be a gradient? If so please explain the gradient. If not ... then why would the effect of anti-gravity be non-linear?

My point is that if it exists everywhere in the same amounts then the effect should appear linear. If I am wrong with this please explain why?

tommac
2009-Dec-01, 10:03 PM
I know you hoped for more based upon your quote : "...would like to see it in action", but that was the best explanation that I could give regarding a mainstream explanation of the results/ effects of GR and the idea of the warping of space.

This is really good stuff and it is actually worded in a way that I get what you are saying ... still maybe not smart enough to wrap my head around it but all you are saying makes sense.

So based on:


There would be no difference between the Earth, a star, or a BH when pictorialized excepting for the increasing "distances between lines" as matter gets closer to the gravity source of larger gravitational influences.


Graphically for a BH, Star, planet or whatever my increasing "distances between lines" as I get closer to the gravity source ...

What I am trying to describe is the opposite of this where as something gets closer to a point there is a decreasing "distance between lines" as you get closer to the point.

so say for this picture:
http://www.astronomynotes.com/evolutn/eclipsgr.gif

instead of the light curving towards the sun ... it would curve away from the sun. So if there was another star directly above the sun we would see in its normal position.


Star
|
\
---------------Earth
Sun
( the |\- are all the path of the light from the stat being pushed away from the sun and hitting the earth. The earth would preceive that light as coming from just about the same direction as the sun. ) I am not saying there are stars that can do this ... just want to know how I can represent this ( repulsive force/anti-gravity) using tensors.

Rather than what is shown in that picture. What I am trying to figure out is how to show that using the ricci tensor or a metric tensor in general

Jeff Root
2009-Dec-02, 02:19 AM
My own impressions of how gravitationally-lensed images would appear if the
gravitational force were repulsive rather than attractive (bottom diagram of
four diagrams):

http://www.freemars.org/jeff/misc/cosmolog/Lensing1.png

-- Jeff, in Minneapolis

WayneFrancis
2009-Dec-02, 02:37 AM
I know that dark matter and dark energy are not the same. Dark matter is what holds universes together and dark energy is like the cosmological constant or the thing we use to explain why the universe is expanding.


Where did you see me say anything about dark matter. Let me say it again.

Gravity/Anti-gravity and Dark energy are NOT the same type of creature.

Nothing about DM in there. I'm just trying to get you off this Dark Energy is like Anti-gravity.



What I am questioning has to do with neither of them. It is just the terminology that I am having problems with.


Well I'm not talking about dark matter either and all you have to do is stop using Anti-gravity where you are talking about Dark Energy.



The question is simple. What is expanding space, and how does expanding space differ from objects moving away from each other.


I don't know how many ways I can say this. Gravity, and one would suppose anti-gravity, move matter through space. Dark energy creates new space.

Once again if you "move" something then there is the concept that while it is getting further away from some things it would be getting closer to others. This does not happen with cosmic inflation/dark energy.



The point that I was trying to make is that when we look at gravity ( didnt say anything about either dark matter or dark energy ) we dont usually say that space is contracting we say that two objects are moving towards each other, although arguably you could say that the space between the two objects is warped.


Note contracting space would be a different then disappearing space. But I don't want to confuse the issue with you any more then it already is.

You've been associating cosmic inflation with anti-gravity this whole thread and this whole thread we've been trying to explain to you that they are not the same. Saying you haven't said anything about dark energy is pretty lame. All anyone needs to do is read the thread and they'll see where you keep throwing in inflation, a.k.a. dark energy, into the discussion.



For the expansion of space however, I am confused why we can only say that space is expanding and we can not say that all objects ( not gravitationally bound ) are moving away from each other .... is there a difference?

YES!

Look take any object around you and move it. Tell me if you where able to move it to a new place without it getting closer to anything else. If you can do this you need to claim your Nobel prise because you've learnt to move objects in another dimension.

WayneFrancis
2009-Dec-02, 02:46 AM
I thought that only when Z=1 that we have unwarped space. Are you saying that the expansion of space is not topological? If it has to do with the topology, then wouldnt it be warped ( in the opposite way of gravity)? Again I am confused about this but not clear on the point that you are making.

Someone can correct me if I'm wrong but I don't look at inflation as a curvature opposite that of gravity. How can anything that is being uniformly changed at every point in space "warp" said space?

At most all it can do is slightly, and uniformly, lessen the effect of gravity on the local scale. You can think of this as a slight "outward pressure". At no point in space, that we can see, is this pressure actually "moving" anything in any particular direction, again I'm ignoring the great attractor.

Think of it as the rubber sheet analogy. I put the bowling ball on the sheet and it causes the gravity well. If I then pull on that sheet in all directions making it larger does the bowling ball move? No The dip/well in the sheet might get slightly more shallow but that is it. Now where the analogy breaks down is DE isn't just continually stretching the sheet it is also adding more rubber to the sheet at every point on the sheet. So while in our analogy the sheet would get "thinner" as it is stretched in reality space/time isn't getting "thinner" It just remains the same thickness as new space is created.

WayneFrancis
2009-Dec-02, 03:19 AM
I am mixing on purpose. My point or rather question was that if anti-gravity (dark energy) was distributed evenly everywhere, then would there be a gradient? If so please explain the gradient. If not ... then why would the effect of anti-gravity be non-linear?

My point is that if it exists everywhere in the same amounts then the effect should appear linear. If I am wrong with this please explain why?

:wall:

You just got saying you aren't talking about DE then right there you equate anti-gravity with dark energy

:wall:

Ok if every point in space had a "anti-gravity" effect to it what would we expect to see....
NOTHING!!!!

run the equations through and you don't get a linear effect. You get NO effect. Just like in the early universe if you have no gravity gradient then it is like there is no gravity at all.

so again
http://latex.codecogs.com/gif.latex?0\textup{d}%20\neq%20n\textup{d}%20\neq% 20\frac{GM}{d^{2}}%20\therefore%20\texttt{gravity/anti-gravity%20at%20every%20point%20in%20space}%20\neq% 20\texttt{dark%20energy/cosmic%20inflation}%20\neq%20\texttt{gravity/anti-gravity%20from%20particular%20points%20in%20space}

Introducing an anti-gravity effect at every point in space is different from introducing a dark energy effect at every point in space.

So STOP CALLING DARK ENERGY ANTI-GRAVITY. They are no more the same then the number "5" is the same as the letter "H" or a "cube" is the same as the colour "red"

For once just do the maths. Spend 15 minutes or so and do the maths to see that gravity/anti-gravity has a different effect then space being created.

WayneFrancis
2009-Dec-02, 03:26 AM
Seeing the last couple of post you are now talking about something other then

Where I really would like to ask is how would the expansion of the universe be different from this? ...

Can we safely assume you are either happy with the fact that the expansion of the universe is not anti-gravity or that you still don't get the difference but don't care about this point any more?

tommac
2009-Dec-02, 05:33 AM
My own impressions of how gravitationally-lensed images would appear if the
gravitational force were repulsive rather than attractive (bottom diagram of
four diagrams):

http://www.freemars.org/jeff/misc/cosmolog/Lensing1.png

-- Jeff, in Minneapolis

Yes I am in agreement ... that is what I was trying to draw using ascii.

tommac
2009-Dec-02, 05:49 AM
Nothing about DM in there. I'm just trying to get you off this Dark Energy is like Anti-gravity.

Fair enough ... but I am trying to discuss your points:


Cosmic inflation
Effect is linear
Effect seems to be increasing over time
Effect seems to be unaffected by mass
Effect does not move object but seems to create "more space"
Effect seems to be repulsive in nature

Cosmic inflation
Effect is linear
I feel that if there was a repulsive energy that the effects could be linear and also (anti-) gravity like if the energy/matter was distributed evenly. This is very similar to the argument in the other thread regarding gradient.

Effect seems to be increasing over time
This is similar to (anti-)gravity right? the effects would increase to infinite time. If gravity has infinite range then anti-gravity would repel/accelerate away with infinite range.


Effect seems to be unaffected by mass
I disagree with this ... because we dont see expansion in gravitationally bound galaxies ... thus it is effected by mass.


Effect does not move object but seems to create "more space"
Other than the > C argument I have not seen the difference.


Effect seems to be repulsive in nature
As would (anti-) gravity.

tommac
2009-Dec-02, 05:54 AM
I don't know how many ways I can say this. Gravity, and one would suppose anti-gravity, move matter through space. Dark energy creates new space.

Are you sure ... I have seen other posts on this board that suggest that objects really continue to move in a straight line. All that gravity does is warp the straight line. Not sure if that is considered "moving an object".

I think it is more accurate to say that gravity moves space that matter is moving through.

tommac
2009-Dec-02, 06:00 AM
Note contracting space would be a different then disappearing space. But I don't want to confuse the issue with you any more then it already is.

Yes and disappearing space would be just about as strange as magically appearing space. Are you saying that the magically appearing space, magically appears in fixed amounts? Otherwise why wouldn't it be topological?

Also if space started appearing in between a galaxy and us ... would its redshift change? You are stating that there is no "movement". Isnt redshift related to movement ?

tommac
2009-Dec-02, 06:05 AM
:wall:

You just got saying you aren't talking about DE then right there you equate anti-gravity with dark energy

I am not saying it. What I am saying is that if whatever it is part of the fabric of space or inherent to space itself then wouldnt it be linear ... as there is no gradient.

tommac
2009-Dec-02, 06:10 AM
Seeing the last couple of post you are now talking about something other then


Can we safely assume you are either happy with the fact that the expansion of the universe is not anti-gravity or that you still don't get the difference but don't care about this point any more?

I am still confused about your points that show the difference. It almost seems that you are arguing that Dark Energy is Anti-gravity but your words are saying that it is absolutely not.

The one point that you have is the expansion of space greater than C.

tommac
2009-Dec-02, 06:18 AM
run the equations through and you don't get a linear effect. You get NO effect. Just like in the early universe if you have no gravity gradient then it is like there is no gravity at all.

Thus the expansion. Thus everything is moving away from everything else. The bread is rising.

Einstein added the Cosmological constant because ( I believe ) he didnt know about the expansion of the universe yet ( hubble? ). He added that into his equations ( please correct me if I am wrong ) because if he didnt the entire universe would contract back into itself. He added the Cosmological Constant to provide universal equilibrium. I would assume that gravity on the universal level still doesnt have a gradient yet einstein predicted its collapse.

WayneFrancis
2009-Dec-02, 11:46 AM
I don't know how many ways I can say this. Gravity, and one would suppose anti-gravity, move matter through space. Dark energy creates new space.
Are you sure ... I have seen other posts on this board that suggest that objects really continue to move in a straight line. All that gravity does is warp the straight line. Not sure if that is considered "moving an object".

I think it is more accurate to say that gravity moves space that matter is moving through.

You are even messing up the concept of gravity even more. So ... when you take a ball and let go it doesn't fall to the ground moving through space in your mind?

What you are saying here is SO far from the mainstream and even fantasy it isn't funny.

WayneFrancis
2009-Dec-02, 11:55 AM
Yes and disappearing space would be just about as strange as magically appearing space. Are you saying that the magically appearing space, magically appears in fixed amounts? Otherwise why wouldn't it be topological?

Also if space started appearing in between a galaxy and us ... would its redshift change? You are stating that there is no "movement". Isnt redshift related to movement ?

Yes, as space is created photons travelling through said space gets it frequency red shifted. The more space the photon travels though (ie the longer it travels) the more red shifted it becomes.

Cosmic red shift isn't from movement it is from inflation. It's effect can look like movement of an object through space but here are 2 important differences.

Movement through space can only show a red shift < 1 or a blue shift < 1
Cosmic inflation can only ever show a red shift > 0

WayneFrancis
2009-Dec-02, 11:59 AM
I am not saying it. What I am saying is that if whatever it is part of the fabric of space or inherent to space itself then wouldnt it be linear ... as there is no gradient.

linear != no gradient.

No gradient = 0 everywhere
Linear = 0 only at a distance of 0, everywhere else linear > 0

WayneFrancis
2009-Dec-02, 12:01 PM
I am still confused about your points that show the difference. It almost seems that you are arguing that Dark Energy is Anti-gravity but your words are saying that it is absolutely not.

The one point that you have is the expansion of space greater than C.

NO, no where have I EVER said ANYTHING remotely like Dark Energy is Anti-gravity.

I've shown you the formulas multiple time. Do you not know/understand what "not equal to" means?

Open your eyes, look at the formulas. DO THE MATHS.

WayneFrancis
2009-Dec-02, 12:17 PM
Thus the expansion. Thus everything is moving away from everything else. The bread is rising.

Einstein added the Cosmological constant because ( I believe ) he didnt know about the expansion of the universe yet ( hubble? ). He added that into his equations ( please correct me if I am wrong ) because if he didnt the entire universe would contract back into itself. He added the Cosmological Constant to provide universal equilibrium. I would assume that gravity on the universal level still doesnt have a gradient yet einstein predicted its collapse.

Ok I understand where you are confused about this. On the very large scale if you picked any average random spot the gravity you feel would be negligible. When I say the early universe had no gravity gradient it is probably better to say that any gravity gradient would be so small that it would be many orders of magnitude < the energy levels of particles that it essentially has no effect. I wouldn't be surprised if we are talking about the same scales as how much the Earth's gravity effect a neutrino speeding away from the sun. Sure there would be an effect but the effect is, for all intensive purposes 0.

Personally if you look at it the Cosmic-logical constant that isn't what DE actually is. The have similar end results but the CC that Einstein introduced does not = Dark Energy. The CC was a number to keep the universe static at the large scale but as we see dark energy doesn't keep the universe static. I know scientist always say the Einstein was right but this is just popular science. It was more that Einstein was on the right track. But if you say that half of America will look at you confused and think that since he didn't get that right then all of his idea might be suspect.

Kwalish Kid
2009-Dec-02, 02:29 PM
Someone can correct me if I'm wrong but I don't look at inflation as a curvature opposite that of gravity. How can anything that is being uniformly changed at every point in space "warp" said space?
You are wrong.

The basis of standard cosmology is that there is a description of spacetime in which all matter can be said to be homogeneously distributed in space. In this model, all of the dynamics of the system are described by a single parameter, the scale factor, which essentially multiplies the average distance between points. (See the Robertson-Walker metric.) The scale factor is a function of time that depends upon the overall density and the cosmological constant/dark energy. (See the Friedmann equation and the Friedmann-Lemaitre equation.) The overall geometry of the model is determined by the effective mass-energy density of the contents, including the effective mass-energy density associated with the cosmological constant.

"Inflation" is a name reserved for a specific type of theory about the very early universe where some inflation field radically increases the scale factor for a time and then stops.

Kwalish Kid
2009-Dec-02, 02:33 PM
Personally if you look at it the Cosmic-logical constant that isn't what DE actually is. The have similar end results but the CC that Einstein introduced does not = Dark Energy. The CC was a number to keep the universe static at the large scale but as we see dark energy doesn't keep the universe static. I know scientist always say the Einstein was right but this is just popular science. It was more that Einstein was on the right track. But if you say that half of America will look at you confused and think that since he didn't get that right then all of his idea might be suspect.
The reasons that Einstein introduced the cosmological constant should not be confused with how it acts. As many of his friends and colleagues pointed out, even with the cosmological constant, Einstein could not keep the universe static (a special term) or unchanging in scale factor as he wished.

When people speak of dark energy, they are usually speaking of the cosmological constant, even when they do not realize this. Attempts have been made to distinguish dark energy from the cosmological constant, but no luck so far.

tommac
2009-Dec-02, 03:02 PM
Yes, as space is created photons travelling through said space gets it frequency red shifted. The more space the photon travels though (ie the longer it travels) the more red shifted it becomes.

So are you saying that light gets tired?
Are you saying that if one galaxy is 1000 light years away and another one is 990 light years away and 10 light years of space was "created" for the one that 990 light years away that both the 1000 light year galaxy and the 990+10 light year galaxy would have the same red-shift?

????

tommac
2009-Dec-02, 03:03 PM
Movement through space can only show a red shift < 1 or a blue shift < 1
Cosmic inflation can only ever show a red shift > 0


Would the speed of gravity play a role here?

Hornblower
2009-Dec-02, 03:06 PM
Would the speed of gravity play a role here?

Why should it?

tommac
2009-Dec-02, 03:06 PM
NO, no where have I EVER said ANYTHING remotely like Dark Energy is Anti-gravity.
.

I know you are Saying that Dark Energy != Anti gravity ... however it seems that the evidence you show to support this statement all suggests that it is.

tommac
2009-Dec-02, 03:07 PM
Why should it?I dont know ... was just asking the question.

tommac
2009-Dec-02, 03:19 PM
Ok I understand where you are confused about this. On the very large scale if you picked any average random spot the gravity you feel would be negligible. When I say the early universe had no gravity gradient it is probably better to say that any gravity gradient would be so small that it would be many orders of magnitude < the energy levels of particles that it essentially has no effect. I wouldn't be surprised if we are talking about the same scales as how much the Earth's gravity effect a neutrino speeding away from the sun. Sure there would be an effect but the effect is, for all intensive purposes 0.

Personally if you look at it the Cosmic-logical constant that isn't what DE actually is. The have similar end results but the CC that Einstein introduced does not = Dark Energy. The CC was a number to keep the universe static at the large scale but as we see dark energy doesn't keep the universe static. I know scientist always say the Einstein was right but this is just popular science. It was more that Einstein was on the right track. But if you say that half of America will look at you confused and think that since he didn't get that right then all of his idea might be suspect.

So we agree here. If space was not expanding, if there was no Dark energy, if there was no cosmological constant the universe would collapse due to gravity right? Is there a gradient?

Lets envision a universe with anti-gravity .... not claiming that it exists ... but lets just envision it for a second, It exists everywhere pushing all energy and matter away from it in places that gravity does not overcome it. The effects would be linear ( except in places where gravity plays a stronger role ) . Everything would be accelerating away from each other ( except where gravity is winning the battle ). Could things move away from each other faster than the speed of light??? maybe ... in a similar way that a BH does ( inside its EH ) ... Mass obviously is effected ...

This all seems to mesh with the points that you show as your evidence. That is why I am still confused.

Kwalish Kid
2009-Dec-02, 03:46 PM
So we agree here. If space was not expanding, if there was no Dark energy, if there was no cosmological constant the universe would collapse due to gravity right?
Whether or not there is dark energy or a cosmological constant, the universe could expand forever. The change in the scale factor over time is slowed by the mass-energy density of the universe, but it can only be slowed to a standstill or reverse into a collapse based on the amount of mass-energy density.

But you should no all this, since you claim to be familiar with basic cosmology texts. I fear that you have mislead us.

Is there a gradient?
What do you mean by "gradient"?

Lets envision a universe with anti-gravity .... not claiming that it exists ... but lets just envision it for a second, It exists everywhere pushing all energy and matter away from it in places that gravity does not overcome it. The effects would be linear ( except in places where gravity plays a stronger role ) . Everything would be accelerating away from each other ( except where gravity is winning the battle ). Could things move away from each other faster than the speed of light??? maybe ... in a similar way that a BH does ( inside its EH ) ... Mass obviously is effected ...

This all seems to mesh with the points that you show as your evidence. That is why I am still confused.
The problem is that you are entirely imagining a force, "anti-gravity" which could have any possible properties that you seem to be fixing arbitrarily. Why not stick to the gravitational theory we already have, since this fits without any need for "anti-gravity". Or you could develop an invisible unicorn theory of gravity.

tommac
2009-Dec-03, 12:10 AM
Whether or not there is dark energy or a cosmological constant, the universe could expand forever. The change in the scale factor over time is slowed by the mass-energy density of the universe, but it can only be slowed to a standstill or reverse into a collapse based on the amount of mass-energy density.
But you should no all this, since you claim to be familiar with basic cosmology texts. I fear that you have mislead us.



Yes I got all of this ... very basic stuff.



What do you mean by "gradient"?

http://en.wikipedia.org/wiki/Gradient
Basically the anti-gravitational field with the direction of movement.




The problem is that you are entirely imagining a force, "anti-gravity" which could have any possible properties that you seem to be fixing arbitrarily. Why not stick to the gravitational theory we already have, since this fits without any need for "anti-gravity". Or you could develop an invisible unicorn theory of gravity.

No I am not making my own rules. I am just taking the opposite of gravity ...
and using a term anti gravity. For me it seems to be very close to what we call Dark Energy ... people are telling me that it is not the same thing ... I am just trying to figure out the differences.

Kwalish Kid
2009-Dec-03, 12:46 AM
Dark energy has a well-defined mathematical relationship to phenomena through gravity as governed by the Einstein Field Equation. It does not simply act as the opposite of gravity, it acts as gravity."Taking the opposite of gravity" could mean anything. Does one take the exact opposite for every particle of matter? Does one take the opposite sign? Does one take the opposite curve in some graph or other?

WayneFrancis
2009-Dec-03, 01:00 AM
Yes, as space is created photons travelling through said space gets it frequency red shifted. The more space the photon travels though (ie the longer it travels) the more red shifted it becomes.
So are you saying that light gets tired?


No tommac I am not saying that. Why to you persist with putting words into my mouth. It is very disingenuous of you. I have made a very clear effort to pick my words in a manner that reduces the chance that someone will misconstrue the actual meaning yet you seem to do that all the time. Please stop "reading between the lines" I do not write in that fashion. Look between my lines and all you should see is white space.

What I'm saying is the cause of cosmic red shift is different from Doppler redshift in that it is due to the space expanding and not do to a normal transfer in momentum and energy.

What is worse is you aren't new to this. We've talked about this stuff before. To pretend that you have no idea what the difference between something moving through space and new space being created really is a tactic that should be beneath you tommac.

So stop trying to put words into my mouth to make it look like I'm trying to support some ATM claim. If we track back almost any ATM type claim in this thread I'll bet you are the source. So far you've tried to blame me for bringing up "Dark Energy", "Dark Matter" and now "Tired Light" in this thread and each time it has been you that bring up these concepts along with many other concepts that are ATM like

...
But when two items attract each other do we consider that the space between them is contracting?...
Trace back. No one every implied that gravity is causes things to come closer together by having space contract. This is you reading something that is pretty clear from a forum member, in this case forrest noble, and reading meanings into their post that are not actually there.

Just stop trying to second guess what people are saying. If forrest noble meant to say that gravity brings 2 objects closer by contracting space between them then forrest noble would have said that. If I meant cosmic redshift is due to "tired light" I would have said that. But you know what I didn't. Nor did anyone else here on this thread.




Are you saying that if one galaxy is 1000 light years away and another one is 990 light years away and 10 light years of space was "created" for the one that 990 light years away that both the 1000 light year galaxy and the 990+10 light year galaxy would have the same red-shift?

????

Once again we see a half baked thought experiment from you that leaves so many holes that if I try to answer your question you'll be able to warp and distort my answer not to fit what you "really" meant.

What I'm saying is that if you have a galaxy that is 1,000ly away and another that is 990 light years away that the one that is 1,000ly away will recede at ~22.688m/s. The one 990ly away will recede at ~22.461m/s. The difference between the 2 recession speed starts at ~227mm/s and will gradually grow over time.

To figure out how much redshift occurs you have to do the following
Take the starting position.
Galaxy A = 1000ly
Take the end position (this is the position the galaxy is when the photon that was released when the galaxy was 1000ly away reaches Earth)
1000ly means that photon travelled for 1000y.
since we are using units of metres and seconds then I'll covert the 1000y to seconds or 31,556,926,000.
I'm going to do a dirty back of the napkin calculation
Since you NEVER do any maths at all I'll assume that you have no problem with me skipping the tedious maths to calculate the distance of a body with increasing acceleration over time.
Over a 1000 years while that photon from the Galaxy A was traveling to the Earth the distance of Galaxy A would increase to a whopping ~1,000.000075679ly
and Galaxy B would be at
~ 990.000074922ly

both of these are a VERY small red shift.

The redshift is basically a comparison of the current distance of an object and distance the object when the photon was emitted. So your question above doesn't actually makes any sense. Cosmic redshift is what it is.

Bear in mind these speeds are slower then the Earth orbits the sun and about 3 orders of magnitude less then the speed our sun orbits around the centre of the galaxy. So detecting the actual redshift is problematic because of proper motion swamping any increase by cosmic inflation.

Again I didn't answer your questions because its about as sensible as asking if I think 5 + red = 7.

WayneFrancis
2009-Dec-03, 01:02 AM
Would the speed of gravity play a role here?

You need to elaborate more. Red/blue shift due to gravity use a completely different formula but are taken into account when measuring cosmic redshifts.

WayneFrancis
2009-Dec-03, 01:10 AM
I know you are Saying that Dark Energy != Anti gravity ... however it seems that the evidence you show to support this statement all suggests that it is.

Please, show me one piece of evidence that supports Dark Energy is the same thing as anti-gravity.

http://latex.codecogs.com/gif.latex?0\textup{d}%20\neq%20n\textup{d}%20\neq% 20\frac{GM}{d^{2}}%20\therefore%20\texttt{gravity/anti-gravity%20at%20every%20point%20in%20space}%20\neq% 20\texttt{dark%20energy/cosmic%20inflation}%20\neq%20\texttt{gravity/anti-gravity%20from%20particular%20points%20in%20space}

Do you understand what "not equal to" means?

I've given you the 3 formulas
0d is essentially what you would have from the effect of anti-gravity uniformly distributed through space
nd = a simplified formula for the effect of dark energy
GM/d2 is the formula for gravity from a point.

the little symbol between those 3 equations means NOT EQUAL TO.

Stop reading what I write, discarding it with out any thought and inserting your own preconceptions into my posts.

YOU ARE THE ONLY ONE SAYING DARK ENERGY IS LIKE ANTI-GRAVITY!

WayneFrancis
2009-Dec-03, 02:38 AM
So we agree here. If space was not expanding, if there was no Dark energy, if there was no cosmological constant the universe would collapse due to gravity right?


If there was no cosmic inflation and then it would be fine to think that the universe might collapse due to gravity. The problem I have with that is that you can take out any attribute of the universe and say "well if this wasn't here then x would happen" We don't live in that type of universe.



Is there a gradient?


Technically there is always a gradient. But it depends on what scale you are looking at on weather it really matters or not. A better way to think of it is a the large scale the universe is flat and you are no more likely to be pulled in 1 direction then you are in any other, again ignoring the great attractor here.

If you go to into one of the great voids technically there is still a slope or gradient of gravity but it is so small you can pretty much ignore it.



Lets envision a universe with anti-gravity .... not claiming that it exists ... but lets just envision it for a second, It exists everywhere pushing all energy and matter away from it in places that gravity does not overcome it. The effects would be linear ( except in places where gravity plays a stronger role ) .


NO IT WOULDN'T BE LINEAR!
The formula for gravity has NO LINEAR COMPONENT TO IT!
NONE, NADA, ZILCH.

If you put anti-gravity in every spot of the universe its net effect everywhere is ZERO NADA ZILCH.

DO THE MATHS!

Or even better. Show us the maths where you can say that an anti-gravity effect would be linear. You know what you can't. You can use the Hubble Law to get a linear effect though. But the Hubble Law has nothing to do with gravity or its so far imaginary counterpart anti-gravity.



Everything would be accelerating away from each other ( except where gravity is winning the battle ). Could things move away from each other faster than the speed of light??? maybe ... in a similar way that a BH does ( inside its EH ) ... Mass obviously is effected ...


Again no, because if the force is evenly distributed then nothing would be moving.

OK lets take this another way.

AG------Object A------Object B

AG = Anti-gravity source.

Object A would be pushed away from AG faster then Object B because the concept of gravity works on a inverse square law. So in the process of Object A moving faster then Object B Object A gets CLOSER to Object B

Now what if AG's effect pushed things that where closer away slower then things that are further away.

Well then true no 2 objects would ever get closer to each other but here are 2 problems

This is AG from a single point (so doesn't apply)
The effect of AG on Object A and Object B IS NOT LINEAR


Now lets take the situation where AG is everywhere. We can simplify this down to a 2D representation

AG------Object A------Object B------AG

Objects A & Object B do NOT move. If you add up all the AG effect coming from the left and all the AG coming from the right they equal.
So no change in locations. It doesn't matter if it works stronger from the source or not.

Gravity doesn't remove space, anti-gravity wouldn't add space, dark energy adds space. There for anti-gravity != Dark Energy



This all seems to mesh with the points that you show as your evidence. That is why I am still confused.

NO IT DOESN'T! Because I have not shown 1 point that says dark energy = anti-gravity. You are confused because you keep reading stuff into my post that I am not actually writing. Stop doing that and you might not be so confused.

WayneFrancis
2009-Dec-03, 02:56 AM
You are wrong.

The basis of standard cosmology is that there is a description of spacetime in which all matter can be said to be homogeneously distributed in space. In this model, all of the dynamics of the system are described by a single parameter, the scale factor, which essentially multiplies the average distance between points. (See the Robertson-Walker metric.) The scale factor is a function of time that depends upon the overall density and the cosmological constant/dark energy. (See the Friedmann equation and the Friedmann-Lemaitre equation.) The overall geometry of the model is determined by the effective mass-energy density of the contents, including the effective mass-energy density associated with the cosmological constant.

"Inflation" is a name reserved for a specific type of theory about the very early universe where some inflation field radically increases the scale factor for a time and then stops.

Yup, thanks got that, but we don't expect what ever dark energy is to stop correct?

WayneFrancis
2009-Dec-03, 03:00 AM
The reasons that Einstein introduced the cosmological constant should not be confused with how it acts. As many of his friends and colleagues pointed out, even with the cosmological constant, Einstein could not keep the universe static (a special term) or unchanging in scale factor as he wished.

When people speak of dark energy, they are usually speaking of the cosmological constant, even when they do not realize this. Attempts have been made to distinguish dark energy from the cosmological constant, but no luck so far.

My point is even if we take out the "why" the actual CC he introduce is not = the effect we see from Dark Energy is it?

IE since the CC Einstein wanted isn't possible and does not = what that dark energy is doing I distinguish the 2 as similar concepts but not the same creature.

WayneFrancis
2009-Dec-03, 03:19 AM
No I am not making my own rules. I am just taking the opposite of gravity ...
and using a term anti gravity. For me it seems to be very close to what we call Dark Energy ... people are telling me that it is not the same thing ... I am just trying to figure out the differences.

YES! Yes you are making up your own rule

the opposite of gravity...hmm
http://latex.codecogs.com/gif.latex?\bg_white%20\150dpi%20g=\frac{GM}{d^{2}}

What is the opposite of that? Something would have to have a negative sign. Lets see....having d be negative doesn't do anything since -d2 = d2
We have never seen anything with negative mass so -M doesn't work. That leave G the gravitational constant. Well because there is still the issue of M in there then the issue is that it couldn't be uniformly everywhere in space since mass isn't uniformly every where in space. Add to this the fact that even if it was every where that mass/energy is all we would see is that there is NO gravity anywhere.

What if -G for anti-gravity is not just the negative of G....still doesn't help. Still have that nasty d2 causing a square law

let me check that square law != linear

12 = 1?....wait yes ....linear so far
22 = 2? Nope ....22 = 4, 4!=2 their for it isn't the same.

DO you mean inverse?

http://latex.codecogs.com/gif.latex?\bg_white%20\150dpi%20g=\frac{d^{2}}{GM}

Well look at that ....still doesn't help. We still have a d2...damn that pesky distance square in the equation.

Ok ... what if the formula for anti-gravity isn't like the formula for gravity and it is just a linear formula? Well then it wouldn't help because if you add up all the forces from 1 direction all the force from the opposite direction would cancel it out. This is the same thing for some "anti-gravity coming from every point in space" even if it a square law. Doesn't matter ... net effect is 0 movement.

Get it out of your head that DE is actually moving anything object THROUGH space. It is NOT!!!!

WayneFrancis
2009-Dec-03, 03:35 AM
Dark energy has a well-defined mathematical relationship to phenomena through gravity as governed by the Einstein Field Equation. It does not simply act as the opposite of gravity, it acts as gravity."Taking the opposite of gravity" could mean anything. Does one take the exact opposite for every particle of matter? Does one take the opposite sign? Does one take the opposite curve in some graph or other?

Ok I know I'm using Newtonian equations but essentially Einstein Field Equation would have the same issue. As you point out we have to figure out what tommac means by opposite.

The fact that tommac refuses to even do simple maths that would produce good approximations I fail to see why bringing up the more complex Einstein Field Equations when the Newtonian law of gravity will do for the scales that he is talking about.

Perhaps tommac can show some maths to describe what he is talking about. Perhaps the sky will turn purple with green and pink dots too...I won't hold my breath for either.

Kwalish Kid
2009-Dec-03, 04:07 AM
Yup, thanks got that, but we don't expect what ever dark energy is to stop correct?
Sho'nuff. In the basic interpretation, because dark energy is to represent the energy of the vacuum, it cannot change. However, there are proposals to have the basis for dark energy be some kind of scalar field. This could change. But there is no evidence that dark energy is different from the basic interpretation.

My point is even if we take out the "why" the actual CC he introduce is not = the effect we see from Dark Energy is it?

IE since the CC Einstein wanted isn't possible and does not = what that dark energy is doing I distinguish the 2 as similar concepts but not the same creature.
I'm not sure what you're saying here. Current cosmology uses dark energy in the equations in the same way that the cosmological constant was used, though without the requirement that the overall behaviour of the scale factor is stasis.

WayneFrancis
2009-Dec-03, 05:19 AM
Sho'nuff. In the basic interpretation, because dark energy is to represent the energy of the vacuum, it cannot change. However, there are proposals to have the basis for dark energy be some kind of scalar field. This could change. But there is no evidence that dark energy is different from the basic interpretation.

I'm not sure what you're saying here. Current cosmology uses dark energy in the equations in the same way that the cosmological constant was used, though without the requirement that the overall behaviour of the scale factor is stasis.

I'm probably just being overly ... ummm what word to use that I won't get in an infraction ... pedantic? no ... anyway
I guess I'm harping on the actual numerical effect of Λ on the EFE back when he introduced it compared to the value we now use as Λ. I still didn't put that into words properly.

I'm not as comfortable doing the maths for tensors and even less trying to convey that back into lay persons talk. In my view when you start talking at that level you should just stay with the mathematical models and steer clear of analogies and simplifications. I.E. its easy to talk about Newtonian gravity with analogies that even a small child can get....2 balls, how much do they weigh and how far apart are they can be grasped by a 5 year old. Explaining EFE with analogies to an average 5 year old....not so easy I would imagine.

Thanks for your corrections. You've pointed out to me some areas I need to focus on with my own knowledge. I'm just wondering why tommac wants to get into tensors given his unwillingness to actually ever do the maths. I'm just scared he'll mess up even more with his "gut feel" maths. I remember him saying that g = ∞ in a looped dimension and we couldn't convince him other wise even when showing him the maths.

tommac
2009-Dec-15, 09:00 PM
OK lets take this another way.

AG------Object A------Object B

AG = Anti-gravity source.

Object A would be pushed away from AG faster then Object B because the concept of gravity works on a inverse square law. So in the process of Object A moving faster then Object B Object A gets CLOSER to Object B

Now what if AG's effect pushed things that where closer away slower then things that are further away.

Well then true no 2 objects would ever get closer to each other but here are 2 problems

This is AG from a single point (so doesn't apply)
The effect of AG on Object A and Object B IS NOT LINEAR


Now lets take the situation where AG is everywhere. We can simplify this down to a 2D representation

AG------Object A------Object B------AG

Objects A & Object B do NOT move. If you add up all the AG effect coming from the left and all the AG coming from the right they equal.
So no change in locations. It doesn't matter if it works stronger from the source or not.

How about this:
+AG1AG2AG3ObjectAAG4AG5AG6ObjectBAG7AG8AG9-

AG1 3+ 6+
AG2 2+ 5+
AG3 1+ 4+
AG4 1- 3+
AG5 2- 2+
AG6 3- 1+
AG7 4- 1-
AG8 5- 2-
AG9 6- 3-

1/3^2 + 1/2^2 + 1/1 - 1/1 -1/2^2 - 1/3^2 - 1/4^2-1/5^2 - 1/6^2 = - 1/4^2 -1/5^2 - 1/6^2

So Object A Would move to the left and Object B would move to the right.

Please correct my math.

tommac
2009-Dec-15, 09:06 PM
We have never seen anything with negative mass so -M doesn't work.

I think I am talking about negative mass or negative energy. So I think I am speaking of -M.

tommac
2009-Dec-15, 09:11 PM
Perhaps tommac can show some maths to describe what he is talking about.


http://latex.codecogs.com/gif.latex?\bg_white%20\150dpi%20g=\frac{GM}{d^{2}}

With M being negative ... you can sub e/C^2 for M with e being negative.

So: d^2 c^2/ e (-)G

tommac
2009-Dec-15, 09:17 PM
I'm just scared he'll mess up even more with his "gut feel" maths. I remember him saying that g = ∞ in a looped dimension and we couldn't convince him other wise even when showing him the maths.
Didn't Einstein do some gut feel maths? He didnt understand how to do the math for GR but he knew what he needed to calculate and the results of the formulae. He had an understanding of what the math did without initially understanding the actual forumlae. Just because I cant calculate exactly the how a tensor works on a topology doesnt mean that I will never understand what a tensor does and when it is needed.

sirius0
2009-Dec-16, 06:05 AM
No Einstein knew his maths and had a gut feel about it. The maths came first. Whereas you have come a gutser over the maths :) !!!!


g=GM/d^2

You have here an attempt to reverse a vector like acceleration using a scalar equation for it's magnitude, meaningless.

Tensor
2009-Dec-16, 02:32 PM
Didn't Einstein do some gut feel maths? He didnt understand how to do the math for GR

See, this is what you get by reading pop-sci accounts and not actually reading the paper. He knew he needed the equations to be covariant. That required tensors. He also needed energy conservation locally. While he didn't understand Absolute Tensor Calculus, at first, he did know and learn from a friend (Marcel Grossman) who did understand. Let's be very clear about this. Einstein did the math himself and found the correct general GR equations (as did David Hilbert separately), by doing the math, manipulating the equations, doing the substitutions and checking the equations were valid. You need to know he was looking for general equations, he was not doing calculations with numbers to find the correct GR equations.


but he knew what he needed to calculate and the results of the formulae. He had an understanding of what the math did without initially understanding the actual forumlae.

This is "not even wrong". Knowing the results you want does not mean you can work back to what the equations should be. You obviously have no clue about the equations of General Relativity. You do realize that the tensor notation hides all manner of complicated math. Here (http://archive.ncsa.illinois.edu/Cyberia/NumRel/mathmine1.html) is an small example (there are only two space dimensions). While you don't need these to calculate Mercury's precession, if you make a change to the current equations, you will change those linked equations. Care to explain how exactly you would check to make sure those equations are correct?


Just because I cant calculate exactly the how a tensor works on a topology doesnt mean that I will never understand what a tensor does and when it is needed.

Well, you will never understand how a tensor "changes" the topology (see, you already got something wrong) of a manifold (BTW, is that manifold a Riemannian, psuedo, or Lorentzian Manifold?), unless you actually study the math. Do you know that you need to differentiate tensors in GR? Exactly how would you know if and when you would have to differentiate, if you actually didn't know the math? Actually, you seem to be very ignorant in the mathematics of GR. Reading up on what tensors are will not give you enough information to make any kind of use of them. Without know the actual mechanisms a tensor actually make use of and represents at a specific time and place, you are pretty much lost.

tommac
2009-Dec-16, 03:59 PM
No Einstein knew his maths and had a gut feel about it. The maths came first. Whereas you have come a gutser over the maths :) !!!!


g=GM/d^2

You have here an attempt to reverse a vector like acceleration using a scalar equation for it's magnitude, meaningless.

No the maths did not come first. in GR he new what he wanted but needed help with the math ... which he did later. He had a "gut feel" abiet and educated "gut feel". The maths get filled in later. I would assume this is what he meant when he said : "I want to know God's thoughts; the rest are details." Gods thoughts = what you are calling "gut feel".

The details are the math.

tommac
2009-Dec-16, 04:03 PM
Ugg ... this thread is not really the place to discuss this ... I am sure there is another thread for you to debate all of this.

However since you are debating it ... Einstein didnt understand Absolute Tensor Calculus right? But he knew that he needed it. he knew the outcome or had an idea of where he was going with it before he did the Tensor Calculus right? The Tensor calculus was the details.




See, this is what you get by reading pop-sci accounts and not actually reading the paper. He knew he needed the equations to be covariant. That required tensors. He also needed energy conservation locally. While he didn't understand Absolute Tensor Calculus, at first, he did know and learn from a friend (Marcel Grossman) who did understand. Let's be very clear about this. Einstein did the math himself and found the correct general GR equations (as did David Hilbert separately), by doing the math, manipulating the equations, doing the substitutions and checking the equations were valid. You need to know he was looking for general equations, he was not doing calculations with numbers to find the correct GR equations.



This is "not even wrong". Knowing the results you want does not mean you can work back to what the equations should be. You obviously have no clue about the equations of General Relativity. You do realize that the tensor notation hides all manner of complicated math. Here (http://archive.ncsa.illinois.edu/Cyberia/NumRel/mathmine1.html) is an small example (there are only two space dimensions). While you don't need these to calculate Mercury's precession, if you make a change to the current equations, you will change those linked equations. Care to explain how exactly you would check to make sure those equations are correct?



Well, you will never understand how a tensor "changes" the topology (see, you already got something wrong) of a manifold (BTW, is that manifold a Riemannian, psuedo, or Lorentzian Manifold?), unless you actually study the math. Do you know that you need to differentiate tensors in GR? Exactly how would you know if and when you would have to differentiate, if you actually didn't know the math? Actually, you seem to be very ignorant in the mathematics of GR. Reading up on what tensors are will not give you enough information to make any kind of use of them. Without know the actual mechanisms a tensor actually make use of and represents at a specific time and place, you are pretty much lost.

tommac
2009-Dec-16, 04:08 PM
Do you know that you need to differentiate tensors in GR? Exactly how would you know if and when you would have to differentiate, if you actually didn't know the math? .

I have abloslutely no interest in learning how to differentiate tensors nor am I sure that i even have the intellectual capacity or attention span to learn this. Alas, I guess I am doomed to be a lost idiot in this world ... :(

tommac
2009-Dec-16, 04:09 PM
Can we please get back on topic:

How about this:
+AG1AG2AG3ObjectAAG4AG5AG6ObjectBAG7AG8AG9-

AG1 3+ 6+
AG2 2+ 5+
AG3 1+ 4+
AG4 1- 3+
AG5 2- 2+
AG6 3- 1+
AG7 4- 1-
AG8 5- 2-
AG9 6- 3-

1/3^2 + 1/2^2 + 1/1 - 1/1 -1/2^2 - 1/3^2 - 1/4^2-1/5^2 - 1/6^2 = - 1/4^2 -1/5^2 - 1/6^2

So Object A Would move to the left and Object B would move to the right.

Please correct my math.



How about this:
+AG1AG2AG3ObjectAAG4AG5AG6ObjectBAG7AG8AG9-

AG1 3+ 6+
AG2 2+ 5+
AG3 1+ 4+
AG4 1- 3+
AG5 2- 2+
AG6 3- 1+
AG7 4- 1-
AG8 5- 2-
AG9 6- 3-

1/3^2 + 1/2^2 + 1/1 - 1/1 -1/2^2 - 1/3^2 - 1/4^2-1/5^2 - 1/6^2 = - 1/4^2 -1/5^2 - 1/6^2

So Object A Would move to the left and Object B would move to the right.

Please correct my math.

Kwalish Kid
2009-Dec-17, 01:32 PM
No the maths did not come first. in GR he new what he wanted but needed help with the math ... which he did later. He had a "gut feel" abiet and educated "gut feel". The maths get filled in later. I would assume this is what he meant when he said : "I want to know God's thoughts; the rest are details." Gods thoughts = what you are calling "gut feel".

The details are the math.
You are confusing the chronological priority with the conceptual priority. For Einstein, if the math couldn't support it, Einstein got rid of it.

Ugg ... this thread is not really the place to discuss this ... I am sure there is another thread for you to debate all of this.

However since you are debating it ... Einstein didnt understand Absolute Tensor Calculus right? But he knew that he needed it. he knew the outcome or had an idea of where he was going with it before he did the Tensor Calculus right? The Tensor calculus was the details.
There is no debate in the historical record that Einstein was amazingly good at mathematics and we instrumental in developing the mathematics that we use for general relativity. Once he had a full theory, he was usually quite clear about what in the theory could actually be supported by the mathematical details and what could not. I believe that this is why he eventually abandoned Mach's principle, which had been a guiding principle in his work.

tommac
2009-Dec-18, 02:51 PM
OK .... I see the flaw in my calculation and agree that the net force is 0 ... however, there would either be an expansion of the entire system or an increase of pressure on the system .... correct?




Can we please get back on topic:

How about this:
+AG1AG2AG3ObjectAAG4AG5AG6ObjectBAG7AG8AG9-

AG1 3+ 6+
AG2 2+ 5+
AG3 1+ 4+
AG4 1- 3+
AG5 2- 2+
AG6 3- 1+
AG7 4- 1-
AG8 5- 2-
AG9 6- 3-

1/3^2 + 1/2^2 + 1/1 - 1/1 -1/2^2 - 1/3^2 - 1/4^2-1/5^2 - 1/6^2 = - 1/4^2 -1/5^2 - 1/6^2

So Object A Would move to the left and Object B would move to the right.

Please correct my math.

frankuitaalst
2009-Dec-25, 10:57 PM
It's a little more complex than just having negative mass. Just looking at Newtonian gravity:
F = G*m1*m2/r^2
A1 = F/m1 = G*m2/r^2
A2 = F/m2 = G*m1/r^2

A negative mass object would experience a force in the opposite direction...but would still accelerate in the same direction in a gravity field around a positive mass. It would however push either positive or negative masses away from it, and a mass and an "antimass" paired together would accelerate indefinitely.
........
.


Right .
Above formulas indicate some odd behaviour of "negative mass " one would not expect .

But ...
- and I hardly dare to formulate the following idea , as I don't want in any case to promote some ATM -
the picture becomes totally different when the known formula F= m* a is slightly modified in F = abs(m) * a.
Where abs(m) is the absolute value of the mass , returning a positive value always , even in the case where the mass m is negative .
In this case equal signed masses always attract ( even "negative" masses ) and opposite signed masses always show a repulsion .

It may be clear that IF such negative mass would exist under this assumption , we never might be able to detect it nearby , as it would have been repelled long time ago .
But also ... it might be difficult to define the kind of mass we are living on today ( positive or negative ?) . If Newtons apple and the Earth would be "negative mass charged" , under this assumption , the apple would fall just as Newton observed .
Again , just a thought .

Jeff Root
2009-Dec-26, 01:08 AM
frankuitaalst,

I said the same in post 17 on November 24
http://www.bautforum.com/1629943-post17.html

Added to it in post 61 on November 30
http://www.bautforum.com/1632989-post61.html
in which I said it appears that the gravitational mass is the
imaginary part of a complex value.

Also post 14 on November 27 in another thread on the same subject
http://www.bautforum.com/1631922-post14.html

-- Jeff, in Minneapolis

frankuitaalst
2009-Dec-26, 09:23 AM
frankuitaalst,

I said the same in post 17 on November 24
http://www.bautforum.com/1629943-post17.html

Added to it in post 61 on November 30
http://www.bautforum.com/1632989-post61.html
in which I said it appears that the gravitational mass is the
imaginary part of a complex value.

Also post 14 on November 27 in another thread on the same subject
http://www.bautforum.com/1631922-post14.html

-- Jeff, in Minneapolis
Indeed you have Jef .
I missed this post 61 . Didn't want to appear pedant .

Edit : I did some googling on "negative mass" , Jeff and found this article .
The author did some simulations on galaxy formation including negative mass .
http://www.triplenine.org/articles/Negative_Mass.htm
Imo the pictures look great

tommac
2009-Dec-27, 09:13 PM
Great link.


I did some googling on "negative mass" , Jeff and found this article .
The author did some simulations on galaxy formation including negative mass .
http://www.triplenine.org/articles/Negative_Mass.htm
Imo the pictures look great

The next thing that interests me though is how a Negative Mass Black Hole ( which would then have to be possible ) interact with positive mass from a relativistic point of view.

tommac
2009-Dec-27, 09:16 PM
Great link.



The next thing that interests me though is how a Negative Mass Black Hole ( which would then have to be possible ) interact with positive mass from a relativistic point of view.

Would it take an infinite amount of energy to "push" positive mass to the EH of a negative energy black hole?

another way to ask this question is would it take an infinite amount of energy to push negative mass into a standard positive mass black hole?

Would time dilation be reversed at the EH of a negative energy black hole? Would time actually move infinitely fast at the EH?

tommac
2009-Dec-28, 03:03 AM
The one part of this article interest me:


The theory appears to be perfectly compatible with the Big Bang, inflation, general relativity, quantum theory, and the Standard Model of particle physics, as well as the latest observations. If it turns out that negative mass does exist, it would solve the problems of large-scale structure and peculiar galactic motion. That would certainly be a matter of some gravity.





Indeed you have Jef .
I missed this post 61 . Didn't want to appear pedant .

Edit : I did some googling on "negative mass" , Jeff and found this article .
The author did some simulations on galaxy formation including negative mass .
http://www.triplenine.org/articles/Negative_Mass.htm
Imo the pictures look great

WayneFrancis
2009-Dec-28, 03:14 AM
OK .... I see the flaw in my calculation and agree that the net force is 0 ... however, there would either be an expansion of the entire system or an increase of pressure on the system .... correct?

How does this follow? How do you extrapolate a net force of 0 as an expansion of the entire system or an increase in pressure?

Lets look at this conceptually.

Lets take the rubber sheet analogy of gravity.

Put the bowling ball in the middle of the sheet and look at the curvature of the sheet. What would AG of the same strength at every point be the equivelant off? How would it change the picture?

It would not have any change. Our maths would still get the same answers that we observe.

Now what do we see with a linear cosmic inflation? The effect is completely different then AG. Here you would get a "pressure" on everything because it is a constant, as it is constantly happening not a constant rate over time, increasing amount of space between objects. This means the distance is constantly increasing so any force that is effected by distance would be effected by this.with a caveat that we don't know enough about DE to say if it actually occurs close to energy

So in theory it would show up in the 4 fundamental forces. But here is the measurement issue. Gravity is already much weaker then the other 3 forces and DE is even weaker then gravity so it isn't going to have much effect on the quantum or classical realms, as we currently understand it.

WayneFrancis
2009-Dec-28, 03:24 AM
Great link.



The next thing that interests me though is how a Negative Mass Black Hole ( which would then have to be possible ) interact with positive mass from a relativistic point of view.

From what I'm hearing it wouldn't. Negative mass would be expected to be attractive to negative mass just as positive mass would be attracted to positive mass. If there was an entire galaxy made up of negative mass would what would we be able to tell?

What would photons from negative mass be like?

For your answer a no positive mass matter would be able to get close to it. Also light would not bend around the object but just bend away from it. Other then that what properties do you think it would have?

WayneFrancis
2009-Dec-28, 03:31 AM
Would it take an infinite amount of energy to "push" positive mass to the EH of a negative energy black hole?

I would say off yes, but that is based on us having a not having a good enough understanding of gravity as is.


another way to ask this question is would it take an infinite amount of energy to push negative mass into a standard positive mass black hole?

Again yes but so what? How much energy does it take to push one of the invisible pink winged unicorns into a black hole?


Would time dilation be reversed at the EH of a negative energy black hole? Would time actually move infinitely fast at the EH?
I would see it as a way to be able to do more. IE if you when towards the NE BH then came back you would experience more time then your twin away from the NE BH. I don't think there would be any travel back in time. So yea time would be infinitely fast at the EH of a BH. I haven't done any maths here and fully acceptance that me conclusions are wrong.

tommac
2009-Dec-28, 04:37 AM
Other then that what properties do you think it would have?

I dont know that is what I am asking.
For example how could I or someone who knew what they were doing tell if the EH of a black hole would appear to have slower time or faster time? so does space-time warp the same way or the opposite way?

By opposite way I mean would time appear to be running faster while lengths appear longer?

At the EH would space time be warped in a way that any positive energy heading towards it be pushed away at the speed of light?

tommac
2009-Dec-28, 04:41 AM
I would say off yes, but that is based on us having a not having a good enough understanding of gravity as is.

Again yes but so what? How much energy does it take to push one of the invisible pink winged unicorns into a black hole?

I would see it as a way to be able to do more. IE if you when towards the NE BH then came back you would experience more time then your twin away from the NE BH. I don't think there would be any travel back in time. So yea time would be infinitely fast at the EH of a BH. I haven't done any maths here and fully acceptance that me conclusions are wrong.

Actually for this I would like to understand the math, but have no clue even where to start.

Don J
2009-Dec-28, 05:26 AM
Negative mass would be even more weird.

Negative mass would accelerate to the left when you push it to the right.

It seem than the existence of negative mass was postulated based on that report...
The Gravitics Situation

Gravity Rand Ltd,
66 Sloan Street
London S.W. 1.

December 1956

Theme of science for 1956-1970:

A Quantum Mechanical Approach to the Existence of Negative Mass and Its Utilization in the Construction of Gravitationally Neutralized Bodies

http://web.archive.org/web/20070908030759/au.geocities.com/psyberplasmic/ccX-3-a2.html

And...
A Link Between Gravitation and Nuclear Energy

http://web.archive.org/web/20070903155922/au.geocities.com/psyberplasmic/ccX-3-a4.html

Jeff Root
2009-Dec-28, 08:22 AM
Thank you for the link, frankuitaalst. His ideas are indeed almost identical
to mine. I have assumed that the matter which has opposite gravity is
antimatter. And I have assumed that it is visible. So I have assumed that
half the galaxies we see are composed of antimatter.

Tom,

My assumption has been that antimatter with antigravity would look exactly
like ordinary matter with ordinary gravity. The physics of everything would
be exactly the same. An antimatter clock falling into an antimatter black
hole would appear to slow down to outside observers. Light from it would
be redshifted. But you are right that it would be impossible for an ordinary
matter object to fall into an antimatter black hole, or for an antimatter
object to fall into an ordinary matter black hole.

-- Jeff, in Minneapolis

frankuitaalst
2009-Dec-28, 11:30 AM
Thank you for the link, frankuitaalst. His ideas are indeed almost identical
to mine. I have assumed that the matter which has opposite gravity is
antimatter. And I have assumed that it is visible. So I have assumed that
half the galaxies we see are composed of antimatter.

Tom,

My assumption has been that antimatter with antigravity would look exactly
like ordinary matter with ordinary gravity. The physics of everything would
be exactly the same. An antimatter clock falling into an antimatter black
hole would appear to slow down to outside observers. Light from it would
be redshifted. But you are right that it would be impossible for an ordinary
matter object to fall into an antimatter black hole, or for an antimatter
object to fall into an ordinary matter black hole.

-- Jeff, in Minneapolis
Jeff , one can also argue in a more general sense : if charge is one property and mass is another property , one can generalize that any combination of mass and charge are possible . This means that negative mass could be accompanied by negative or positive charge , just as ordinary matter ( positive mass ) can have negative or positive charge .
This generalisation also has symmetry .

An interestng article about the possible consequences of negative mass can be found here ( freely available )
http://vixra.org/pdf/0907.0015v8.pdf

tusenfem
2009-Dec-28, 12:37 PM
Jeff , one can also argue in a more general sense : if charge is one property and mass is another property , one can generalize that any combination of mass and charge are possible . This means that negative mass could be accompanied by negative or positive charge , just as ordinary matter ( positive mass ) can have negative or positive charge .
This generalisation also has symmetry .

An interestng article about the possible consequences of negative mass can be found here ( freely available )
http://vixra.org/pdf/0907.0015v8.pdf

Well, that can straight go to ATM.
And why is Eq. (1) of that paper already wrong?

DrRocket
2009-Dec-28, 12:57 PM
It seem than the existence of negative mass was postulated based on that report...
The Gravitics Situation

Gravity Rand Ltd,
66 Sloan Street
London S.W. 1.

December 1956

Theme of science for 1956-1970:

A Quantum Mechanical Approach to the Existence of Negative Mass and Its Utilization in the Construction of Gravitationally Neutralized Bodies

http://web.archive.org/web/20070908030759/au.geocities.com/psyberplasmic/ccX-3-a2.html

And...
A Link Between Gravitation and Nuclear Energy

http://web.archive.org/web/20070903155922/au.geocities.com/psyberplasmic/ccX-3-a4.html


These links appear to be pure ATM garbage.

tusenfem
2009-Dec-28, 02:02 PM
I now took a look at the links that DrRocket quoted from Don J. Apparently, this thread is now really sliding off in the ATM, and as this is Q&A, I therefore close this thread.